diff --git a/benches/bench_log.rs b/benches/bench_log.rs
old mode 100755
new mode 100644
index e35c53cb..9a6b3fc5
--- a/benches/bench_log.rs
+++ b/benches/bench_log.rs
@@ -6,9 +6,7 @@ extern crate serde;
 extern crate "rustc-serialize" as rustc_serialize;
 extern crate test;
 
-use std::old_io::ByRefWriter;
-use std::old_io::extensions::Bytes;
-use std::old_io;
+use std::io::{self, ReadExt, WriteExt};
 use std::num::FromPrimitive;
 use test::Bencher;
 
@@ -616,10 +614,15 @@ impl MyMemWriter0 {
 }
 
 
-impl Writer for MyMemWriter0 {
+impl io::Write for MyMemWriter0 {
     #[inline]
-    fn write_all(&mut self, buf: &[u8]) -> old_io::IoResult<()> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         self.buf.push_all(buf);
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
         Ok(())
     }
 }
@@ -656,10 +659,15 @@ fn push_all_bytes(dst: &mut Vec<u8>, src: &[u8]) {
     }
 }
 
-impl Writer for MyMemWriter1 {
+impl io::Write for MyMemWriter1 {
     #[inline]
-    fn write_all(&mut self, buf: &[u8]) -> old_io::IoResult<()> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         push_all_bytes(&mut self.buf, buf);
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
         Ok(())
     }
 }
@@ -759,7 +767,7 @@ fn bench_serializer_slice(b: &mut Bencher) {
 
     b.iter(|| {
         for item in buf.iter_mut(){ *item = 0; }
-        let mut wr = std::old_io::BufWriter::new(&mut buf);
+        let mut wr = &mut buf[];
 
         let mut serializer = json::Serializer::new(wr.by_ref());
         log.serialize(&mut serializer).unwrap();
@@ -839,166 +847,166 @@ fn bench_copy(b: &mut Bencher) {
     });
 }
 
-fn manual_serialize_no_escape<W: Writer>(wr: &mut W, log: &Log) {
-    wr.write_str("{\"timestamp\":").unwrap();
+fn manual_serialize_no_escape<W: io::Write>(wr: &mut W, log: &Log) {
+    (write!(wr, "{{\"timestamp\":")).unwrap();
     (write!(wr, "{}", log.timestamp)).unwrap();
-    wr.write_str(",\"zone_id\":").unwrap();
+    (write!(wr, ",\"zone_id\":")).unwrap();
     (write!(wr, "{}", log.zone_id)).unwrap();
-    wr.write_str(",\"zone_plan\":").unwrap();
+    (write!(wr, ",\"zone_plan\":")).unwrap();
     (write!(wr, "{}", log.zone_plan as usize)).unwrap();
 
-    wr.write_str(",\"http\":{\"protocol\":").unwrap();
+    (write!(wr, ",\"http\":{{\"protocol\":")).unwrap();
     (write!(wr, "{}", log.http.protocol as usize)).unwrap();
-    wr.write_str(",\"status\":").unwrap();
+    (write!(wr, ",\"status\":")).unwrap();
     (write!(wr, "{}", log.http.status)).unwrap();
-    wr.write_str(",\"host_status\":").unwrap();
+    (write!(wr, ",\"host_status\":")).unwrap();
     (write!(wr, "{}", log.http.host_status)).unwrap();
-    wr.write_str(",\"up_status\":").unwrap();
+    (write!(wr, ",\"up_status\":")).unwrap();
     (write!(wr, "{}", log.http.up_status)).unwrap();
-    wr.write_str(",\"method\":").unwrap();
+    (write!(wr, ",\"method\":")).unwrap();
     (write!(wr, "{}", log.http.method as usize)).unwrap();
-    wr.write_str(",\"content_type\":").unwrap();
+    (write!(wr, ",\"content_type\":")).unwrap();
     (write!(wr, "\"{}\"", log.http.content_type)).unwrap();
-    wr.write_str(",\"user_agent\":").unwrap();
+    (write!(wr, ",\"user_agent\":")).unwrap();
     (write!(wr, "\"{}\"", log.http.user_agent)).unwrap();
-    wr.write_str(",\"referer\":").unwrap();
+    (write!(wr, ",\"referer\":")).unwrap();
     (write!(wr, "\"{}\"", log.http.referer)).unwrap();
-    wr.write_str(",\"request_uri\":").unwrap();
+    (write!(wr, ",\"request_uri\":")).unwrap();
     (write!(wr, "\"{}\"", log.http.request_uri)).unwrap();
 
-    wr.write_str("},\"origin\":{").unwrap();
+    (write!(wr, "}},\"origin\":{{")).unwrap();
 
-    wr.write_str("\"ip\":").unwrap();
+    (write!(wr, "\"ip\":")).unwrap();
     (write!(wr, "\"{}\"", log.origin.ip)).unwrap();
-    wr.write_str(",\"port\":").unwrap();
+    (write!(wr, ",\"port\":")).unwrap();
     (write!(wr, "{}", log.origin.port)).unwrap();
-    wr.write_str(",\"hostname\":").unwrap();
+    (write!(wr, ",\"hostname\":")).unwrap();
     (write!(wr, "\"{}\"", log.origin.hostname)).unwrap();
 
-    wr.write_str(",\"protocol\":").unwrap();
+    (write!(wr, ",\"protocol\":")).unwrap();
     (write!(wr, "{}", log.origin.protocol as usize)).unwrap();
 
-    wr.write_str("},\"country\":").unwrap();
+    (write!(wr, "}},\"country\":")).unwrap();
     (write!(wr, "{}", log.country as usize)).unwrap();
-    wr.write_str(",\"cache_status\":").unwrap();
+    (write!(wr, ",\"cache_status\":")).unwrap();
     (write!(wr, "{}", log.cache_status as usize)).unwrap();
-    wr.write_str(",\"server_ip\":").unwrap();
+    (write!(wr, ",\"server_ip\":")).unwrap();
     (write!(wr, "\"{}\"", log.server_ip)).unwrap();
-    wr.write_str(",\"server_name\":").unwrap();
+    (write!(wr, ",\"server_name\":")).unwrap();
     (write!(wr, "\"{}\"", log.server_name)).unwrap();
-    wr.write_str(",\"remote_ip\":").unwrap();
+    (write!(wr, ",\"remote_ip\":")).unwrap();
     (write!(wr, "\"{}\"", log.remote_ip)).unwrap();
-    wr.write_str(",\"bytes_dlv\":").unwrap();
+    (write!(wr, ",\"bytes_dlv\":")).unwrap();
     (write!(wr, "{}", log.bytes_dlv)).unwrap();
 
-    wr.write_str(",\"ray_id\":").unwrap();
+    (write!(wr, ",\"ray_id\":")).unwrap();
     (write!(wr, "\"{}\"", log.ray_id)).unwrap();
-    wr.write_str("}").unwrap();
+    (write!(wr, "}}")).unwrap();
 }
 
-fn manual_serialize_escape<W: Writer>(wr: &mut W, log: &Log) {
-    wr.write_str("{").unwrap();
+fn manual_serialize_escape<W: io::Write>(wr: &mut W, log: &Log) {
+    (write!(wr, "{{")).unwrap();
     escape_str(wr, "timestamp").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.timestamp)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "zone_id").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.zone_id)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "zone_plan").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.zone_plan as isize)).unwrap();
 
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "http").unwrap();
-    wr.write_str(":{").unwrap();
+    (write!(wr, ":{{")).unwrap();
     escape_str(wr, "protocol").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.http.protocol as usize)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "status").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.http.status)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "host_status").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.http.host_status)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "up_status").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.http.up_status)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "method").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.http.method as usize)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "content_type").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.http.content_type).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "user_agent").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.http.user_agent).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "referer").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.http.referer).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "request_uri").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.http.request_uri).unwrap();
 
-    wr.write_str("},").unwrap();
+    (write!(wr, "}},")).unwrap();
     escape_str(wr, "origin").unwrap();
-    wr.write_str(":{").unwrap();
+    (write!(wr, ":{{")).unwrap();
 
     escape_str(wr, "ip").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.origin.ip).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "port").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.origin.port)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "hostname").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.origin.hostname).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "protocol").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.origin.protocol as usize)).unwrap();
 
-    wr.write_str("},").unwrap();
+    (write!(wr, "}},")).unwrap();
     escape_str(wr, "country").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.country as usize)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "cache_status").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.cache_status as usize)).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "server_ip").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.server_ip).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "server_name").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.server_name).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "remote_ip").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.remote_ip).unwrap();
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "bytes_dlv").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     (write!(wr, "{}", log.bytes_dlv)).unwrap();
 
-    wr.write_str(",").unwrap();
+    (write!(wr, ",")).unwrap();
     escape_str(wr, "ray_id").unwrap();
-    wr.write_str(":").unwrap();
+    (write!(wr, ":")).unwrap();
     escape_str(wr, &log.ray_id).unwrap();
-    wr.write_str("}").unwrap();
+    (write!(wr, "}}")).unwrap();
 }
 
 #[test]
@@ -1156,7 +1164,7 @@ fn bench_manual_serialize_my_mem_writer1_escape(b: &mut Bencher) {
     });
 }
 
-fn direct<W: Writer>(wr: &mut W, log: &Log) {
+fn direct<W: io::Write>(wr: &mut W, log: &Log) {
     use serde::ser::Serializer;
 
     let mut serializer = json::Serializer::new(wr.by_ref());
@@ -1653,9 +1661,8 @@ fn bench_iter_manual_iter_deserializers(b: &mut Bencher) {
 
 #[test]
 fn test_iter_manual_reader_as_iter_deserializer() {
-    let mut rdr = JSON_STR.as_bytes();
-    let iter = Bytes::new(&mut rdr)
-        .map(|x| x.unwrap());
+    let rdr = JSON_STR.as_bytes();
+    let iter = rdr.bytes().map(|x| x.unwrap());
 
     let log = manual_iter_deserialize(iter);
 
@@ -1667,9 +1674,8 @@ fn bench_iter_manual_reader_as_iter_deserializer(b: &mut Bencher) {
     b.bytes = JSON_STR.len() as u64;
 
     b.iter(|| {
-        let mut rdr = JSON_STR.as_bytes();
-        let iter = Bytes::new(&mut rdr)
-            .map(|x| x.unwrap());
+        let rdr = JSON_STR.as_bytes();
+        let iter = rdr.bytes().map(|x| x.unwrap());
 
         let _ = manual_iter_deserialize(iter);
     });
@@ -1680,9 +1686,8 @@ fn bench_iter_manual_reader_as_iter_deserializers(b: &mut Bencher) {
     b.bytes = JSON_STR.len() as u64;
 
     for _ in range(0is, 10000) {
-        let mut rdr = JSON_STR.as_bytes();
-        let iter = Bytes::new(&mut rdr)
-            .map(|x| x.unwrap());
+        let rdr = JSON_STR.as_bytes();
+        let iter = rdr.bytes().map(|x| x.unwrap());
 
         let _ = manual_iter_deserialize(iter);
     }
diff --git a/src/json/error.rs b/src/json/error.rs
index a6598004..6df233e3 100644
--- a/src/json/error.rs
+++ b/src/json/error.rs
@@ -1,6 +1,6 @@
 use std::error;
 use std::fmt;
-use std::old_io;
+use std::io;
 
 use de::{Token, TokenKind};
 
@@ -82,7 +82,7 @@ impl fmt::Debug for ErrorCode {
 pub enum Error {
     /// msg, line, col
     SyntaxError(ErrorCode, usize, usize),
-    IoError(old_io::IoError),
+    IoError(io::Error),
     ExpectedError(String, String),
     MissingFieldError(String),
     UnknownVariantError(String),
@@ -120,8 +120,8 @@ impl fmt::Display for Error {
     }
 }
 
-impl error::FromError<old_io::IoError> for Error {
-    fn from_error(error: old_io::IoError) -> Error {
+impl error::FromError<io::Error> for Error {
+    fn from_error(error: io::Error) -> Error {
         Error::IoError(error)
     }
 }
diff --git a/src/json/mod.rs b/src/json/mod.rs
index dc387734..51c85fc1 100644
--- a/src/json/mod.rs
+++ b/src/json/mod.rs
@@ -65,7 +65,7 @@ To serialize using `Serialize`:
 
 extern crate serde;
 
-use std::old_io::ByRefWriter;
+use std::io::WriteExt;
 use serde::json;
 use serde::Serialize;
 
diff --git a/src/json/ser.rs b/src/json/ser.rs
index 6ace7f03..2892934d 100644
--- a/src/json/ser.rs
+++ b/src/json/ser.rs
@@ -1,14 +1,14 @@
 use std::f32;
 use std::f64;
 use std::num::{Float, FpCategory};
-use std::old_io::{IoError, IoResult};
+use std::io;
 use std::string::FromUtf8Error;
 
 use ser::Serialize;
 use ser;
 
-fn escape_bytes<W: Writer>(wr: &mut W, bytes: &[u8]) -> IoResult<()> {
-    try!(wr.write_str("\""));
+fn escape_bytes<W: io::Write>(wr: &mut W, bytes: &[u8]) -> io::Result<()> {
+    try!(write!(wr, "\""));
 
     let mut start = 0;
 
@@ -28,7 +28,7 @@ fn escape_bytes<W: Writer>(wr: &mut W, bytes: &[u8]) -> IoResult<()> {
             try!(wr.write_all(&bytes[start..i]));
         }
 
-        try!(wr.write_str(escaped));
+        try!(write!(wr, "{}", escaped));
 
         start = i + 1;
     }
@@ -37,34 +37,34 @@ fn escape_bytes<W: Writer>(wr: &mut W, bytes: &[u8]) -> IoResult<()> {
         try!(wr.write_all(&bytes[start..]));
     }
 
-    wr.write_str("\"")
+    write!(wr, "\"")
 }
 
-pub fn escape_str<W: Writer>(wr: &mut W, v: &str) -> IoResult<()> {
+pub fn escape_str<W: io::Write>(wr: &mut W, v: &str) -> io::Result<()> {
     escape_bytes(wr, v.as_bytes())
 }
 
-fn escape_char<W: Writer>(wr: &mut W, v: char) -> IoResult<()> {
+fn escape_char<W: io::Write>(wr: &mut W, v: char) -> io::Result<()> {
     let buf = &mut [0; 4];
     v.encode_utf8(buf);
     escape_bytes(wr, buf)
 }
 
-fn fmt_f32_or_null<W: Writer>(wr: &mut W, v: f32) -> IoResult<()> {
+fn fmt_f32_or_null<W: io::Write>(wr: &mut W, v: f32) -> io::Result<()> {
     match v.classify() {
-        FpCategory::Nan | FpCategory::Infinite => wr.write_str("null"),
-        _ => wr.write_str(&f32::to_str_digits(v, 6)),
+        FpCategory::Nan | FpCategory::Infinite => write!(wr, "null"),
+        _ => write!(wr, "{}", f32::to_str_digits(v, 6)),
     }
 }
 
-fn fmt_f64_or_null<W: Writer>(wr: &mut W, v: f64) -> IoResult<()> {
+fn fmt_f64_or_null<W: io::Write>(wr: &mut W, v: f64) -> io::Result<()> {
     match v.classify() {
-        FpCategory::Nan | FpCategory::Infinite => wr.write_str("null"),
-        _ => wr.write_str(&f64::to_str_digits(v, 6)),
+        FpCategory::Nan | FpCategory::Infinite => write!(wr, "null"),
+        _ => write!(wr, "{}", f64::to_str_digits(v, 6)),
     }
 }
 
-fn spaces<W: Writer>(wr: &mut W, mut n: usize) -> IoResult<()> {
+fn spaces<W: io::Write>(wr: &mut W, mut n: usize) -> io::Result<()> {
     const LEN: usize = 16;
     const BUF: &'static [u8; LEN] = &[b' '; LEN];
 
@@ -96,7 +96,7 @@ pub struct Serializer<W> {
     first: bool,
 }
 
-impl<W: Writer> Serializer<W> {
+impl<W: io::Write> Serializer<W> {
     /// Creates a new JSON serializer whose output will be written to the writer
     /// specified.
     pub fn new(wr: W) -> Serializer<W> {
@@ -106,174 +106,174 @@ impl<W: Writer> Serializer<W> {
         }
     }
 
-    /// Unwrap the Writer from the Serializer.
+    /// Unwrap the io::Write from the Serializer.
     pub fn unwrap(self) -> W {
         self.wr
     }
 }
 
-impl<W: Writer> ser::Serializer<IoError> for Serializer<W> {
+impl<W: io::Write> ser::Serializer<io::Error> for Serializer<W> {
     #[inline]
-    fn serialize_null(&mut self) -> IoResult<()> {
-        self.wr.write_str("null")
+    fn serialize_null(&mut self) -> io::Result<()> {
+        write!(&mut self.wr, "null")
     }
 
     #[inline]
-    fn serialize_bool(&mut self, v: bool) -> IoResult<()> {
+    fn serialize_bool(&mut self, v: bool) -> io::Result<()> {
         if v {
-            self.wr.write_str("true")
+            write!(&mut self.wr, "true")
         } else {
-            self.wr.write_str("false")
+            write!(&mut self.wr, "false")
         }
     }
 
     #[inline]
-    fn serialize_isize(&mut self, v: isize) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_isize(&mut self, v: isize) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i8(&mut self, v: i8) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i8(&mut self, v: i8) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i16(&mut self, v: i16) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i16(&mut self, v: i16) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i32(&mut self, v: i32) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i32(&mut self, v: i32) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i64(&mut self, v: i64) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i64(&mut self, v: i64) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_usize(&mut self, v: usize) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_usize(&mut self, v: usize) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u8(&mut self, v: u8) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u8(&mut self, v: u8) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u16(&mut self, v: u16) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u16(&mut self, v: u16) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u32(&mut self, v: u32) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u32(&mut self, v: u32) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u64(&mut self, v: u64) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u64(&mut self, v: u64) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_f32(&mut self, v: f32) -> IoResult<()> {
+    fn serialize_f32(&mut self, v: f32) -> io::Result<()> {
         fmt_f32_or_null(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_f64(&mut self, v: f64) -> IoResult<()> {
+    fn serialize_f64(&mut self, v: f64) -> io::Result<()> {
         fmt_f64_or_null(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_char(&mut self, v: char) -> IoResult<()> {
+    fn serialize_char(&mut self, v: char) -> io::Result<()> {
         escape_char(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_str(&mut self, v: &str) -> IoResult<()> {
+    fn serialize_str(&mut self, v: &str) -> io::Result<()> {
         escape_str(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_tuple_start(&mut self, _len: usize) -> IoResult<()> {
+    fn serialize_tuple_start(&mut self, _len: usize) -> io::Result<()> {
         self.first = true;
-        self.wr.write_str("[")
+        write!(&mut self.wr, "[")
     }
 
     #[inline]
     fn serialize_tuple_elt<
-        T: Serialize<Serializer<W>, IoError>
-    >(&mut self, value: &T) -> IoResult<()> {
+        T: Serialize<Serializer<W>, io::Error>
+    >(&mut self, value: &T) -> io::Result<()> {
         if self.first {
             self.first = false;
         } else {
-            try!(self.wr.write_str(","));
+            try!(write!(&mut self.wr, ","));
         }
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_tuple_end(&mut self) -> IoResult<()> {
-        self.wr.write_str("]")
+    fn serialize_tuple_end(&mut self) -> io::Result<()> {
+        write!(&mut self.wr, "]")
     }
 
     #[inline]
-    fn serialize_struct_start(&mut self, _name: &str, _len: usize) -> IoResult<()> {
+    fn serialize_struct_start(&mut self, _name: &str, _len: usize) -> io::Result<()> {
         self.first = true;
-        self.wr.write_str("{")
+        write!(&mut self.wr, "{{")
     }
 
     #[inline]
     fn serialize_struct_elt<
-        T: Serialize<Serializer<W>, IoError>
-    >(&mut self, name: &str, value: &T) -> IoResult<()> {
+        T: Serialize<Serializer<W>, io::Error>
+    >(&mut self, name: &str, value: &T) -> io::Result<()> {
         if self.first {
             self.first = false;
         } else {
-            try!(self.wr.write_str(","));
+            try!(write!(&mut self.wr, ","));
         }
         try!(name.serialize(self));
-        try!(self.wr.write_str(":"));
+        try!(write!(&mut self.wr, ":"));
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_struct_end(&mut self) -> IoResult<()> {
-        self.wr.write_str("}")
+    fn serialize_struct_end(&mut self) -> io::Result<()> {
+        write!(&mut self.wr, "}}")
     }
 
     #[inline]
-    fn serialize_enum_start(&mut self, _name: &str, variant: &str, _len: usize) -> IoResult<()> {
+    fn serialize_enum_start(&mut self, _name: &str, variant: &str, _len: usize) -> io::Result<()> {
         self.first = true;
-        try!(self.wr.write_str("{"));
+        try!(write!(&mut self.wr, "{{"));
         try!(self.serialize_str(variant));
-        self.wr.write_str(":[")
+        write!(&mut self.wr, ":[")
     }
 
     #[inline]
     fn serialize_enum_elt<
-        T: Serialize<Serializer<W>, IoError>
-    >(&mut self, value: &T) -> IoResult<()> {
+        T: Serialize<Serializer<W>, io::Error>
+    >(&mut self, value: &T) -> io::Result<()> {
         if self.first {
             self.first = false;
         } else {
-            try!(self.wr.write_str(","));
+            try!(write!(&mut self.wr, ","));
         }
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_enum_end(&mut self) -> IoResult<()> {
-        self.wr.write_str("]}")
+    fn serialize_enum_end(&mut self) -> io::Result<()> {
+        write!(&mut self.wr, "]}}")
     }
 
     #[inline]
     fn serialize_option<
-        T: Serialize<Serializer<W>, IoError>
-    >(&mut self, v: &Option<T>) -> IoResult<()> {
+        T: Serialize<Serializer<W>, io::Error>
+    >(&mut self, v: &Option<T>) -> io::Result<()> {
         match *v {
             Some(ref v) => {
                 v.serialize(self)
@@ -286,42 +286,42 @@ impl<W: Writer> ser::Serializer<IoError> for Serializer<W> {
 
     #[inline]
     fn serialize_seq<
-        T: Serialize<Serializer<W>, IoError>,
+        T: Serialize<Serializer<W>, io::Error>,
         Iter: Iterator<Item=T>
-    >(&mut self, iter: Iter) -> IoResult<()> {
-        try!(self.wr.write_str("["));
+    >(&mut self, iter: Iter) -> io::Result<()> {
+        try!(write!(&mut self.wr, "["));
         let mut first = true;
         for elt in iter {
             if first {
                 first = false;
             } else {
-                try!(self.wr.write_str(","));
+                try!(write!(&mut self.wr, ","));
             }
             try!(elt.serialize(self));
 
         }
-        self.wr.write_str("]")
+        write!(&mut self.wr, "]")
     }
 
     #[inline]
     fn serialize_map<
-        K: Serialize<Serializer<W>, IoError>,
-        V: Serialize<Serializer<W>, IoError>,
+        K: Serialize<Serializer<W>, io::Error>,
+        V: Serialize<Serializer<W>, io::Error>,
         Iter: Iterator<Item=(K, V)>
-    >(&mut self, iter: Iter) -> IoResult<()> {
-        try!(self.wr.write_str("{"));
+    >(&mut self, iter: Iter) -> io::Result<()> {
+        try!(write!(&mut self.wr, "{{"));
         let mut first = true;
         for (key, value) in iter {
             if first {
                 first = false;
             } else {
-                try!(self.wr.write_str(","));
+                try!(write!(&mut self.wr, ","));
             }
             try!(key.serialize(self));
-            try!(self.wr.write_str(":"));
+            try!(write!(&mut self.wr, ":"));
             try!(value.serialize(self));
         }
-        self.wr.write_str("}")
+        write!(&mut self.wr, "}}")
     }
 }
 
@@ -333,7 +333,7 @@ pub struct PrettySerializer<W> {
     first: bool,
 }
 
-impl<W: Writer> PrettySerializer<W> {
+impl<W: io::Write> PrettySerializer<W> {
     /// Creates a new serializer whose output will be written to the specified writer
     pub fn new(wr: W) -> PrettySerializer<W> {
         PrettySerializer {
@@ -343,191 +343,191 @@ impl<W: Writer> PrettySerializer<W> {
         }
     }
 
-    /// Unwrap the Writer from the Serializer.
+    /// Unwrap the io::Write from the Serializer.
     pub fn unwrap(self) -> W {
         self.wr
     }
 
     #[inline]
-    fn serialize_sep(&mut self) -> IoResult<()> {
+    fn serialize_sep(&mut self) -> io::Result<()> {
         if self.first {
             self.first = false;
             self.indent += 2;
-            try!(self.wr.write_str("\n"));
+            try!(write!(&mut self.wr, "\n"));
         } else {
-            try!(self.wr.write_str(",\n"));
+            try!(write!(&mut self.wr, ",\n"));
         }
 
         spaces(&mut self.wr, self.indent)
     }
 
     #[inline]
-    fn serialize_end(&mut self, s: &str) -> IoResult<()> {
+    fn serialize_end(&mut self, s: &str) -> io::Result<()> {
         if !self.first {
-            try!(self.wr.write_str("\n"));
+            try!(write!(&mut self.wr, "\n"));
             self.indent -= 2;
             try!(spaces(&mut self.wr, self.indent));
         }
 
         self.first = false;
 
-        self.wr.write_str(s)
+        write!(&mut self.wr, "{}", s)
     }
 }
 
-impl<W: Writer> ser::Serializer<IoError> for PrettySerializer<W> {
+impl<W: io::Write> ser::Serializer<io::Error> for PrettySerializer<W> {
     #[inline]
-    fn serialize_null(&mut self) -> IoResult<()> {
-        self.wr.write_str("null")
+    fn serialize_null(&mut self) -> io::Result<()> {
+        write!(&mut self.wr, "null")
     }
 
     #[inline]
-    fn serialize_bool(&mut self, v: bool) -> IoResult<()> {
+    fn serialize_bool(&mut self, v: bool) -> io::Result<()> {
         if v {
-            self.wr.write_str("true")
+            write!(&mut self.wr, "true")
         } else {
-            self.wr.write_str("false")
+            write!(&mut self.wr, "false")
         }
     }
 
     #[inline]
-    fn serialize_isize(&mut self, v: isize) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_isize(&mut self, v: isize) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i8(&mut self, v: i8) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i8(&mut self, v: i8) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i16(&mut self, v: i16) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i16(&mut self, v: i16) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i32(&mut self, v: i32) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i32(&mut self, v: i32) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_i64(&mut self, v: i64) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_i64(&mut self, v: i64) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_usize(&mut self, v: usize) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_usize(&mut self, v: usize) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u8(&mut self, v: u8) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u8(&mut self, v: u8) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u16(&mut self, v: u16) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u16(&mut self, v: u16) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u32(&mut self, v: u32) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u32(&mut self, v: u32) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_u64(&mut self, v: u64) -> IoResult<()> {
-        write!(&mut self.wr, "{}", v)
+    fn serialize_u64(&mut self, v: u64) -> io::Result<()> {
+        write!(&mut &mut self.wr, "{}", v)
     }
 
     #[inline]
-    fn serialize_f32(&mut self, v: f32) -> IoResult<()> {
+    fn serialize_f32(&mut self, v: f32) -> io::Result<()> {
         fmt_f32_or_null(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_f64(&mut self, v: f64) -> IoResult<()> {
+    fn serialize_f64(&mut self, v: f64) -> io::Result<()> {
         fmt_f64_or_null(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_char(&mut self, v: char) -> IoResult<()> {
+    fn serialize_char(&mut self, v: char) -> io::Result<()> {
         escape_char(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_str(&mut self, v: &str) -> IoResult<()> {
+    fn serialize_str(&mut self, v: &str) -> io::Result<()> {
         escape_str(&mut self.wr, v)
     }
 
     #[inline]
-    fn serialize_tuple_start(&mut self, _len: usize) -> IoResult<()> {
+    fn serialize_tuple_start(&mut self, _len: usize) -> io::Result<()> {
         self.first = true;
-        self.wr.write_str("[")
+        write!(&mut self.wr, "[")
     }
 
     #[inline]
     fn serialize_tuple_elt<
-        T: Serialize<PrettySerializer<W>, IoError>
-    >(&mut self, value: &T) -> IoResult<()> {
+        T: Serialize<PrettySerializer<W>, io::Error>
+    >(&mut self, value: &T) -> io::Result<()> {
         try!(self.serialize_sep());
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_tuple_end(&mut self) -> IoResult<()> {
+    fn serialize_tuple_end(&mut self) -> io::Result<()> {
         self.serialize_end("]")
     }
 
     #[inline]
-    fn serialize_struct_start(&mut self, _name: &str, _len: usize) -> IoResult<()> {
+    fn serialize_struct_start(&mut self, _name: &str, _len: usize) -> io::Result<()> {
         self.first = true;
-        self.wr.write_str("{")
+        write!(&mut self.wr, "{{")
     }
 
     #[inline]
     fn serialize_struct_elt<
-        T: Serialize<PrettySerializer<W>, IoError>
-    >(&mut self, name: &str, value: &T) -> IoResult<()> {
+        T: Serialize<PrettySerializer<W>, io::Error>
+    >(&mut self, name: &str, value: &T) -> io::Result<()> {
         try!(self.serialize_sep());
         try!(self.serialize_str(name));
-        try!(self.wr.write_str(": "));
+        try!(write!(&mut self.wr, ": "));
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_struct_end(&mut self) -> IoResult<()> {
+    fn serialize_struct_end(&mut self) -> io::Result<()> {
         self.serialize_end("}")
     }
 
     #[inline]
-    fn serialize_enum_start(&mut self, _name: &str, variant: &str, _len: usize) -> IoResult<()> {
+    fn serialize_enum_start(&mut self, _name: &str, variant: &str, _len: usize) -> io::Result<()> {
         self.first = true;
-        try!(self.wr.write_str("{"));
+        try!(write!(&mut self.wr, "{{"));
         try!(self.serialize_sep());
         try!(self.serialize_str(variant));
         self.first = true;
-        self.wr.write_str(": [")
+        write!(&mut self.wr, ": [")
     }
 
     #[inline]
     fn serialize_enum_elt<
-        T: Serialize<PrettySerializer<W>, IoError>
-    >(&mut self, value: &T) -> IoResult<()> {
+        T: Serialize<PrettySerializer<W>, io::Error>
+    >(&mut self, value: &T) -> io::Result<()> {
         try!(self.serialize_sep());
         value.serialize(self)
     }
 
     #[inline]
-    fn serialize_enum_end(&mut self) -> IoResult<()> {
+    fn serialize_enum_end(&mut self) -> io::Result<()> {
         try!(self.serialize_tuple_end());
         self.serialize_struct_end()
     }
 
     #[inline]
     fn serialize_option<
-        T: Serialize<PrettySerializer<W>, IoError>
-    >(&mut self, v: &Option<T>) -> IoResult<()> {
+        T: Serialize<PrettySerializer<W>, io::Error>
+    >(&mut self, v: &Option<T>) -> io::Result<()> {
         match *v {
             Some(ref v) => {
                 v.serialize(self)
@@ -540,10 +540,10 @@ impl<W: Writer> ser::Serializer<IoError> for PrettySerializer<W> {
 
     #[inline]
     fn serialize_seq<
-        T: Serialize<PrettySerializer<W>, IoError>,
+        T: Serialize<PrettySerializer<W>, io::Error>,
         Iter: Iterator<Item=T>
-    >(&mut self, iter: Iter) -> IoResult<()> {
-        try!(self.wr.write_str("["));
+    >(&mut self, iter: Iter) -> io::Result<()> {
+        try!(write!(&mut self.wr, "["));
 
         self.first = true;
         for elt in iter {
@@ -556,17 +556,17 @@ impl<W: Writer> ser::Serializer<IoError> for PrettySerializer<W> {
 
     #[inline]
     fn serialize_map<
-        K: Serialize<PrettySerializer<W>, IoError>,
-        V: Serialize<PrettySerializer<W>, IoError>,
+        K: Serialize<PrettySerializer<W>, io::Error>,
+        V: Serialize<PrettySerializer<W>, io::Error>,
         Iter: Iterator<Item=(K, V)>
-    >(&mut self, iter: Iter) -> IoResult<()> {
-        try!(self.wr.write_str("{"));
+    >(&mut self, iter: Iter) -> io::Result<()> {
+        try!(write!(&mut self.wr, "{{"));
 
         self.first = true;
         for (key, value) in iter {
             try!(self.serialize_sep());
             try!(key.serialize(self));
-            try!(self.wr.write_str(": "));
+            try!(write!(&mut self.wr, ": "));
             try!(value.serialize(self));
         }
 
@@ -577,9 +577,9 @@ impl<W: Writer> ser::Serializer<IoError> for PrettySerializer<W> {
 /// Encode the specified struct into a json `[u8]` writer.
 #[inline]
 pub fn to_writer<
-    W: Writer,
-    T: Serialize<Serializer<W>, IoError>
->(writer: W, value: &T) -> IoResult<W> {
+    W: io::Write,
+    T: Serialize<Serializer<W>, io::Error>
+>(writer: W, value: &T) -> io::Result<W> {
     let mut serializer = Serializer::new(writer);
     try!(value.serialize(&mut serializer));
     Ok(serializer.unwrap())
@@ -588,7 +588,7 @@ pub fn to_writer<
 /// Encode the specified struct into a json `[u8]` buffer.
 #[inline]
 pub fn to_vec<
-    T: Serialize<Serializer<Vec<u8>>, IoError>
+    T: Serialize<Serializer<Vec<u8>>, io::Error>
 >(value: &T) -> Vec<u8> {
     // We are writing to a Vec, which doesn't fail. So we can ignore
     // the error.
@@ -599,7 +599,7 @@ pub fn to_vec<
 /// Encode the specified struct into a json `String` buffer.
 #[inline]
 pub fn to_string<
-    T: Serialize<Serializer<Vec<u8>>, IoError>
+    T: Serialize<Serializer<Vec<u8>>, io::Error>
 >(value: &T) -> Result<String, FromUtf8Error> {
     let buf = to_vec(value);
     String::from_utf8(buf)
@@ -608,9 +608,9 @@ pub fn to_string<
 /// Encode the specified struct into a json `[u8]` writer.
 #[inline]
 pub fn to_pretty_writer<
-    W: Writer,
-    T: Serialize<PrettySerializer<W>, IoError>
->(writer: W, value: &T) -> IoResult<W> {
+    W: io::Write,
+    T: Serialize<PrettySerializer<W>, io::Error>
+>(writer: W, value: &T) -> io::Result<W> {
     let mut serializer = PrettySerializer::new(writer);
     try!(value.serialize(&mut serializer));
     Ok(serializer.unwrap())
@@ -618,7 +618,7 @@ pub fn to_pretty_writer<
 
 /// Encode the specified struct into a json `[u8]` buffer.
 pub fn to_pretty_vec<
-    T: Serialize<PrettySerializer<Vec<u8>>, IoError>
+    T: Serialize<PrettySerializer<Vec<u8>>, io::Error>
 >(value: &T) -> Vec<u8> {
     // We are writing to a Vec, which doesn't fail. So we can ignore
     // the error.
@@ -628,7 +628,7 @@ pub fn to_pretty_vec<
 
 /// Encode the specified struct into a json `String` buffer.
 pub fn to_pretty_string<
-    T: Serialize<PrettySerializer<Vec<u8>>, IoError>
+    T: Serialize<PrettySerializer<Vec<u8>>, io::Error>
 >(value: &T) -> Result<String, FromUtf8Error> {
     let buf = to_pretty_vec(value);
     String::from_utf8(buf)
diff --git a/src/json/value.rs b/src/json/value.rs
index 9dc80b8f..ef540787 100644
--- a/src/json/value.rs
+++ b/src/json/value.rs
@@ -1,7 +1,6 @@
 use std::collections::{HashMap, BTreeMap, btree_map};
 use std::fmt;
-use std::old_io::{ByRefWriter, IoResult};
-use std::old_io;
+use std::io::{self, WriteExt};
 use std::str;
 use std::string::ToString;
 use std::vec;
@@ -27,14 +26,14 @@ pub enum Value {
 
 impl Value {
     /// Serializes a json value into an io::writer.  Uses a single line.
-    pub fn to_writer<W: Writer>(&self, wr: W) -> IoResult<()> {
+    pub fn to_writer<W: io::Write>(&self, wr: W) -> io::Result<()> {
         let mut serializer = Serializer::new(wr);
         self.serialize(&mut serializer)
     }
 
     /// Serializes a json value into an io::writer.
     /// Pretty-prints in a more readable format.
-    pub fn to_pretty_writer<W: Writer>(&self, wr: W) -> IoResult<()> {
+    pub fn to_pretty_writer<W: io::Write>(&self, wr: W) -> io::Result<()> {
         let mut serializer = PrettySerializer::new(wr);
         self.serialize(&mut serializer)
     }
@@ -220,9 +219,16 @@ struct WriterFormatter<'a, 'b: 'a> {
     inner: &'a mut fmt::Formatter<'b>,
 }
 
-impl<'a, 'b> Writer for WriterFormatter<'a, 'b> {
-    fn write_all(&mut self, buf: &[u8]) -> IoResult<()> {
-        self.inner.write_str(str::from_utf8(buf).unwrap()).map_err(|_| old_io::IoError::last_error())
+impl<'a, 'b> io::Write for WriterFormatter<'a, 'b> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        match self.inner.write_str(str::from_utf8(buf).unwrap()) {
+            Ok(_) => Ok(buf.len()),
+            Err(_) => Err(io::Error::last_os_error()),
+        }
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
     }
 }
 
diff --git a/tests/json.rs b/tests/json.rs
index 5131fb06..30978c79 100644
--- a/tests/json.rs
+++ b/tests/json.rs
@@ -7,7 +7,7 @@ extern crate test;
 extern crate serde;
 
 use std::fmt::Debug;
-use std::old_io;
+use std::io;
 use std::str;
 use std::string;
 use std::collections::BTreeMap;
@@ -113,7 +113,7 @@ impl ToJson for Outer {
 }
 
 fn test_encode_ok<
-    T: PartialEq + Debug + ToJson + ser::Serialize<json::Serializer<Vec<u8>>, old_io::IoError>
+    T: PartialEq + Debug + ToJson + ser::Serialize<json::Serializer<Vec<u8>>, io::Error>
 >(errors: &[(T, &str)]) {
     for &(ref value, out) in errors {
         let out = out.to_string();
@@ -127,7 +127,7 @@ fn test_encode_ok<
 }
 
 fn test_pretty_encode_ok<
-    T: PartialEq + Debug + ToJson + ser::Serialize<json::PrettySerializer<Vec<u8>>, old_io::IoError>
+    T: PartialEq + Debug + ToJson + ser::Serialize<json::PrettySerializer<Vec<u8>>, io::Error>
 >(errors: &[(T, &str)]) {
     for &(ref value, out) in errors {
         let out = out.to_string();