diff --git a/src/libstd/sys/common/thread.rs b/src/libstd/sys/common/thread.rs
index 16f4f01bf39fe..7f288e593a35b 100644
--- a/src/libstd/sys/common/thread.rs
+++ b/src/libstd/sys/common/thread.rs
@@ -14,11 +14,11 @@ use alloc::boxed::FnBox;
 use libc;
 use sys::stack_overflow;
 
-pub unsafe fn start_thread(main: *mut libc::c_void) {
+pub unsafe fn start_thread(main: *mut libc::c_void, id: u32) {
     // Next, set up our stack overflow handler which may get triggered if we run
     // out of stack.
     let _handler = stack_overflow::Handler::new();
 
     // Finally, let's run some code.
-    Box::from_raw(main as *mut Box<FnBox()>)()
+    Box::from_raw(main as *mut Box<FnBox(u32)>)(id)
 }
diff --git a/src/libstd/sys/unix/thread.rs b/src/libstd/sys/unix/thread.rs
index b7968e9344f3c..2358bdf67c77e 100644
--- a/src/libstd/sys/unix/thread.rs
+++ b/src/libstd/sys/unix/thread.rs
@@ -35,7 +35,7 @@ unsafe impl Send for Thread {}
 unsafe impl Sync for Thread {}
 
 impl Thread {
-    pub unsafe fn new<'a>(stack: usize, p: Box<FnBox() + 'a>)
+    pub unsafe fn new<'a>(stack: usize, p: Box<FnBox(u32) + 'a>)
                           -> io::Result<Thread> {
         let p = box p;
         let mut native: libc::pthread_t = mem::zeroed();
@@ -71,7 +71,7 @@ impl Thread {
         };
 
         extern fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
-            unsafe { start_thread(main); }
+            unsafe { start_thread(main, pthread_self() as u32); }
             ptr::null_mut()
         }
     }
@@ -162,6 +162,10 @@ impl Thread {
             debug_assert_eq!(ret, 0);
         }
     }
+
+    pub fn id(&self) -> u32 {
+        self.id as u32
+    }
 }
 
 impl Drop for Thread {
diff --git a/src/libstd/sys/windows/thread.rs b/src/libstd/sys/windows/thread.rs
index cf1b3ebddb97b..ec60759797d59 100644
--- a/src/libstd/sys/windows/thread.rs
+++ b/src/libstd/sys/windows/thread.rs
@@ -49,7 +49,7 @@ impl Thread {
         };
 
         extern "system" fn thread_start(main: *mut libc::c_void) -> DWORD {
-            unsafe { start_thread(main); }
+            unsafe { start_thread(main, 42); }
             0
         }
     }
@@ -78,6 +78,10 @@ impl Thread {
             c::Sleep(super::dur2timeout(dur))
         }
     }
+
+    pub fn id(&self) -> u32 {
+        42 // TODO
+    }
 }
 
 pub mod guard {
diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs
index 9b8f63997b642..abe1bc98867b0 100644
--- a/src/libstd/thread/mod.rs
+++ b/src/libstd/thread/mod.rs
@@ -252,17 +252,18 @@ impl Builder {
 
         let stack_size = stack_size.unwrap_or(util::min_stack());
 
-        let my_thread = Thread::new(name);
-        let their_thread = my_thread.clone();
+        let mut my_thread = Thread::new(name);
+        let mut their_thread = my_thread.clone();
 
         let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
             = Arc::new(UnsafeCell::new(None));
         let their_packet = my_packet.clone();
 
-        let main = move || {
+        let main = move |id: u32| {
             if let Some(name) = their_thread.name() {
                 imp::Thread::set_name(name);
             }
+            their_thread.id = id;
             unsafe {
                 thread_info::set(imp::guard::current(), their_thread);
                 let mut output = None;
@@ -276,10 +277,12 @@ impl Builder {
             }
         };
 
+        let native = unsafe {
+            try!(imp::Thread::new(stack_size, Box::new(main)))
+        };
+        my_thread.id = native.id();
         Ok(JoinHandle(JoinInner {
-            native: unsafe {
-                Some(try!(imp::Thread::new(stack_size, Box::new(main))))
-            },
+            native: Some(native),
             thread: my_thread,
             packet: Packet(my_packet),
         }))
@@ -502,6 +505,7 @@ struct Inner {
 /// A handle to a thread.
 pub struct Thread {
     inner: Arc<Inner>,
+    id: u32,
 }
 
 impl Thread {
@@ -512,7 +516,8 @@ impl Thread {
                 name: name,
                 lock: Mutex::new(false),
                 cvar: Condvar::new(),
-            })
+            }),
+            id: 0,
         }
     }
 
@@ -533,12 +538,20 @@ impl Thread {
     pub fn name(&self) -> Option<&str> {
         self.inner.name.as_ref().map(|s| &**s)
     }
+
+    /// Gets the thread's unique ID.
+    ///
+    /// This ID is unique across running threads, and a thread that has stopped
+    /// might see its ID reused.
+    pub fn id(&self) -> u32 {
+        self.id
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for Thread {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::Debug::fmt(&self.name(), f)
+        fmt::Debug::fmt(&self.name(), f)  // print ID?
     }
 }