diff --git a/doc/rust.texi b/doc/rust.texi
index fcca023d2553e..bc7562088971c 100644
--- a/doc/rust.texi
+++ b/doc/rust.texi
@@ -2930,6 +2930,7 @@ effects of the expression's evaluation.
 * Ref.Expr.Ret::                Expression for stopping and producing a value.
 @c * Ref.Expr.Be::                 Expression for stopping and executing a tail call.
 * Ref.Expr.Put::                Expression for pausing and producing a value.
+* Ref.Expr.As::                 Expression for casting a value to a different type.
 * Ref.Expr.Fail::               Expression for causing task failure.
 * Ref.Expr.Log::                Expression for logging values to diagnostic buffers.
 * Ref.Expr.Note::               Expression for logging values during failure.
@@ -3116,6 +3117,30 @@ either continuing execution after the @code{put} expression, or terminating its
 execution and destroying the iterator frame.
 
 
+@node       Ref.Expr.As
+@subsection Ref.Expr.As
+@c * Ref.Expr.As::                 Expression for casting a value to a different type.
+@cindex As expression
+@cindex Cast
+@cindex Typecast
+
+Executing an @code{as} expression casts the value on the left-hand side to the
+type on the right-hand side.
+
+A numeric value can be cast to any numeric type.  A native pointer value can
+be cast to or from any integral type or native pointer type.  Any other cast
+is unsupported and will fail to compiler.
+
+An example of an @code{as} expression:
+@example
+fn avg(v: [float]) -> float @{
+  let sum: float = sum(v);
+  let sz: float = std::vec::len(v) as float;
+  ret sum / sz;
+@}
+@end example
+
+
 @node       Ref.Expr.Fail
 @subsection Ref.Expr.Fail
 @c * Ref.Expr.Fail::               Expression for causing task failure.
diff --git a/src/test/compile-fail/nonscalar-cast.rs b/src/test/compile-fail/nonscalar-cast.rs
new file mode 100644
index 0000000000000..ab920550f44c3
--- /dev/null
+++ b/src/test/compile-fail/nonscalar-cast.rs
@@ -0,0 +1,8 @@
+// error-pattern:non-scalar cast
+
+use std;
+import std::os;
+
+fn main() {
+  log { x: 1 } as int;
+}
diff --git a/src/test/compile-fail/unsupported-cast.rs b/src/test/compile-fail/unsupported-cast.rs
new file mode 100644
index 0000000000000..00e65f4024018
--- /dev/null
+++ b/src/test/compile-fail/unsupported-cast.rs
@@ -0,0 +1,8 @@
+// error-pattern:unsupported cast
+
+use std;
+import std::os;
+
+fn main() {
+  log 1.0 as os::libc::FILE; // Can't cast float to native.
+}
diff --git a/src/test/run-pass/supported-cast.rs b/src/test/run-pass/supported-cast.rs
new file mode 100644
index 0000000000000..a100386d1dcbb
--- /dev/null
+++ b/src/test/run-pass/supported-cast.rs
@@ -0,0 +1,253 @@
+use std;
+import std::os;
+
+fn main() {
+  let f = 1 as os::libc::FILE;
+  log f as int;
+  log f as uint;
+  log f as i8;
+  log f as i16;
+  log f as i32;
+  log f as i64;
+  log f as u8;
+  log f as u16;
+  log f as u32;
+  log f as u64;
+
+  log 1 as int;
+  log 1 as uint;
+  log 1 as float;
+  log 1 as bool;
+  log 1 as os::libc::FILE;
+  log 1 as i8;
+  log 1 as i16;
+  log 1 as i32;
+  log 1 as i64;
+  log 1 as u8;
+  log 1 as u16;
+  log 1 as u32;
+  log 1 as u64;
+  log 1 as f32;
+  log 1 as f64;
+
+  log 1u as int;
+  log 1u as uint;
+  log 1u as float;
+  log 1u as bool;
+  log 1u as os::libc::FILE;
+  log 1u as i8;
+  log 1u as i16;
+  log 1u as i32;
+  log 1u as i64;
+  log 1u as u8;
+  log 1u as u16;
+  log 1u as u32;
+  log 1u as u64;
+  log 1u as f32;
+  log 1u as f64;
+
+  log 1i8 as int;
+  log 1i8 as uint;
+  log 1i8 as float;
+  log 1i8 as bool;
+  log 1i8 as os::libc::FILE;
+  log 1i8 as i8;
+  log 1i8 as i16;
+  log 1i8 as i32;
+  log 1i8 as i64;
+  log 1i8 as u8;
+  log 1i8 as u16;
+  log 1i8 as u32;
+  log 1i8 as u64;
+  log 1i8 as f32;
+  log 1i8 as f64;
+
+  log 1u8 as int;
+  log 1u8 as uint;
+  log 1u8 as float;
+  log 1u8 as bool;
+  log 1u8 as os::libc::FILE;
+  log 1u8 as i8;
+  log 1u8 as i16;
+  log 1u8 as i32;
+  log 1u8 as i64;
+  log 1u8 as u8;
+  log 1u8 as u16;
+  log 1u8 as u32;
+  log 1u8 as u64;
+  log 1u8 as f32;
+  log 1u8 as f64;
+
+  log 1i16 as int;
+  log 1i16 as uint;
+  log 1i16 as float;
+  log 1i16 as bool;
+  log 1i16 as os::libc::FILE;
+  log 1i16 as i8;
+  log 1i16 as i16;
+  log 1i16 as i32;
+  log 1i16 as i64;
+  log 1i16 as u8;
+  log 1i16 as u16;
+  log 1i16 as u32;
+  log 1i16 as u64;
+  log 1i16 as f32;
+  log 1i16 as f64;
+
+  log 1u16 as int;
+  log 1u16 as uint;
+  log 1u16 as float;
+  log 1u16 as bool;
+  log 1u16 as os::libc::FILE;
+  log 1u16 as i8;
+  log 1u16 as i16;
+  log 1u16 as i32;
+  log 1u16 as i64;
+  log 1u16 as u8;
+  log 1u16 as u16;
+  log 1u16 as u32;
+  log 1u16 as u64;
+  log 1u16 as f32;
+  log 1u16 as f64;
+
+  log 1i32 as int;
+  log 1i32 as uint;
+  log 1i32 as float;
+  log 1i32 as bool;
+  log 1i32 as os::libc::FILE;
+  log 1i32 as i8;
+  log 1i32 as i16;
+  log 1i32 as i32;
+  log 1i32 as i64;
+  log 1i32 as u8;
+  log 1i32 as u16;
+  log 1i32 as u32;
+  log 1i32 as u64;
+  log 1i32 as f32;
+  log 1i32 as f64;
+
+  log 1u32 as int;
+  log 1u32 as uint;
+  log 1u32 as float;
+  log 1u32 as bool;
+  log 1u32 as os::libc::FILE;
+  log 1u32 as i8;
+  log 1u32 as i16;
+  log 1u32 as i32;
+  log 1u32 as i64;
+  log 1u32 as u8;
+  log 1u32 as u16;
+  log 1u32 as u32;
+  log 1u32 as u64;
+  log 1u32 as f32;
+  log 1u32 as f64;
+
+  log 1i64 as int;
+  log 1i64 as uint;
+  log 1i64 as float;
+  log 1i64 as bool;
+  log 1i64 as os::libc::FILE;
+  log 1i64 as i8;
+  log 1i64 as i16;
+  log 1i64 as i32;
+  log 1i64 as i64;
+  log 1i64 as u8;
+  log 1i64 as u16;
+  log 1i64 as u32;
+  log 1i64 as u64;
+  log 1i64 as f32;
+  log 1i64 as f64;
+
+  log 1u64 as int;
+  log 1u64 as uint;
+  log 1u64 as float;
+  log 1u64 as bool;
+  log 1u64 as os::libc::FILE;
+  log 1u64 as i8;
+  log 1u64 as i16;
+  log 1u64 as i32;
+  log 1u64 as i64;
+  log 1u64 as u8;
+  log 1u64 as u16;
+  log 1u64 as u32;
+  log 1u64 as u64;
+  log 1u64 as f32;
+  log 1u64 as f64;
+
+  log 1u64 as int;
+  log 1u64 as uint;
+  log 1u64 as float;
+  log 1u64 as bool;
+  log 1u64 as os::libc::FILE;
+  log 1u64 as i8;
+  log 1u64 as i16;
+  log 1u64 as i32;
+  log 1u64 as i64;
+  log 1u64 as u8;
+  log 1u64 as u16;
+  log 1u64 as u32;
+  log 1u64 as u64;
+  log 1u64 as f32;
+  log 1u64 as f64;
+
+  log true as int;
+  log true as uint;
+  log true as float;
+  log true as bool;
+  log true as os::libc::FILE;
+  log true as i8;
+  log true as i16;
+  log true as i32;
+  log true as i64;
+  log true as u8;
+  log true as u16;
+  log true as u32;
+  log true as u64;
+  log true as f32;
+  log true as f64;
+
+  log 1. as int;
+  log 1. as uint;
+  log 1. as float;
+  log 1. as bool;
+  log 1. as i8;
+  log 1. as i16;
+  log 1. as i32;
+  log 1. as i64;
+  log 1. as u8;
+  log 1. as u16;
+  log 1. as u32;
+  log 1. as u64;
+  log 1. as f32;
+  log 1. as f64;
+
+  log 1f32 as int;
+  log 1f32 as uint;
+  log 1f32 as float;
+  log 1f32 as bool;
+  log 1f32 as i8;
+  log 1f32 as i16;
+  log 1f32 as i32;
+  log 1f32 as i64;
+  log 1f32 as u8;
+  log 1f32 as u16;
+  log 1f32 as u32;
+  log 1f32 as u64;
+  log 1f32 as f32;
+  log 1f32 as f64;
+
+  log 1f64 as int;
+  log 1f64 as uint;
+  log 1f64 as float;
+  log 1f64 as bool;
+  log 1f64 as i8;
+  log 1f64 as i16;
+  log 1f64 as i32;
+  log 1f64 as i64;
+  log 1f64 as u8;
+  log 1f64 as u16;
+  log 1f64 as u32;
+  log 1f64 as u64;
+  log 1f64 as f32;
+  log 1f64 as f64;
+}