diff --git a/src/libserialize/base64.rs b/src/libserialize/base64.rs
index c999157b89a..e69a0ea7929 100644
--- a/src/libserialize/base64.rs
+++ b/src/libserialize/base64.rs
@@ -13,6 +13,7 @@
 //! Base64 binary-to-text encoding
 use std::fmt;
 use std::string;
+use std::error;
 
 /// Available encoding character sets
 pub enum CharacterSet {
@@ -178,6 +179,19 @@ impl fmt::Show for FromBase64Error {
     }
 }
 
+impl error::Error for FromBase64Error {
+    fn description(&self) -> &str {
+        match *self {
+            InvalidBase64Byte(_, _) => "invalid character",
+            InvalidBase64Length => "invalid length",
+        }
+    }
+
+    fn detail(&self) -> Option<String> {
+        Some(self.to_string())
+    }
+}
+
 impl<'a> FromBase64 for &'a str {
     /**
      * Convert any base64 encoded string (literal, `@`, `&`, or `~`)
diff --git a/src/libserialize/hex.rs b/src/libserialize/hex.rs
index ffe63f738cf..b591d35c67c 100644
--- a/src/libserialize/hex.rs
+++ b/src/libserialize/hex.rs
@@ -13,6 +13,7 @@
 //! Hex binary-to-text encoding
 use std::fmt;
 use std::string;
+use std::error;
 
 /// A trait for converting a value to hexadecimal encoding
 pub trait ToHex {
@@ -77,6 +78,20 @@ impl fmt::Show for FromHexError {
     }
 }
 
+impl error::Error for FromHexError {
+    fn description(&self) -> &str {
+        match *self {
+            InvalidHexCharacter(_, _) => "invalid character",
+            InvalidHexLength => "invalid length",
+        }
+    }
+
+    fn detail(&self) -> Option<String> {
+        Some(self.to_string())
+    }
+}
+
+
 impl<'a> FromHex for &'a str {
     /**
      * Convert any hexadecimal encoded string (literal, `@`, `&`, or `~`)
diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index 06f934c075d..cde2dfac378 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -313,6 +313,11 @@ fn io_error_to_error(io: io::IoError) -> ParserError {
     IoError(io.kind, io.desc)
 }
 
+impl std::error::Error for DecoderError {
+    fn description(&self) -> &str { "decoder error" }
+    fn detail(&self) -> Option<std::string::String> { Some(self.to_string()) }
+}
+
 pub type EncodeResult = io::IoResult<()>;
 pub type DecodeResult<T> = Result<T, DecoderError>;
 
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index c6f237ff1da..3dcd8d792a4 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -222,7 +222,9 @@ responding to errors that may occur while attempting to read the numbers.
 #![deny(unused_must_use)]
 
 use char::Char;
+use clone::Clone;
 use default::Default;
+use error::{FromError, Error};
 use fmt;
 use int;
 use iter::Iterator;
@@ -433,6 +435,22 @@ impl fmt::Show for IoError {
     }
 }
 
+impl Error for IoError {
+    fn description(&self) -> &str {
+        self.desc
+    }
+
+    fn detail(&self) -> Option<String> {
+        self.detail.clone()
+    }
+}
+
+impl FromError<IoError> for Box<Error> {
+    fn from_error(err: IoError) -> Box<Error> {
+        box err
+    }
+}
+
 /// A list specifying general categories of I/O error.
 #[deriving(PartialEq, Eq, Clone, Show)]
 pub enum IoErrorKind {
diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index 5b3c872d2b7..9846f7b653e 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -32,11 +32,13 @@
 #![allow(non_snake_case)]
 
 use clone::Clone;
+use error::{FromError, Error};
 use fmt;
 use io::{IoResult, IoError};
 use iter::Iterator;
 use libc::{c_void, c_int};
 use libc;
+use boxed::Box;
 use ops::Drop;
 use option::{Some, None, Option};
 use os;
@@ -48,6 +50,7 @@ use slice::{AsSlice, ImmutableSlice, MutableSlice, ImmutablePartialEqSlice};
 use slice::CloneableVector;
 use str::{Str, StrSlice, StrAllocating};
 use string::String;
+use to_string::ToString;
 use sync::atomic::{AtomicInt, INIT_ATOMIC_INT, SeqCst};
 use vec::Vec;
 
@@ -1437,6 +1440,17 @@ impl fmt::Show for MapError {
     }
 }
 
+impl Error for MapError {
+    fn description(&self) -> &str { "memory map error" }
+    fn detail(&self) -> Option<String> { Some(self.to_string()) }
+}
+
+impl FromError<MapError> for Box<Error> {
+    fn from_error(err: MapError) -> Box<Error> {
+        box err
+    }
+}
+
 #[cfg(unix)]
 impl MemoryMap {
     /// Create a new mapping with the given `options`, at least `min_len` bytes