diff --git a/src/libcore/core.rc b/src/libcore/core.rc
index 913832a7f07..f1ceeff9ea8 100644
--- a/src/libcore/core.rc
+++ b/src/libcore/core.rc
@@ -39,7 +39,7 @@ export float, f32, f64;
 export box, char, str, ptr, vec, bool;
 export either, option, result, iter;
 export libc, os, io, run, rand, sys, unsafe, logging;
-export arc, comm, task, future;
+export comm, task, future;
 export extfmt;
 export tuple;
 export to_str;
@@ -175,7 +175,6 @@ mod dvec_iter {
 }
 
 // Concurrency
-mod arc;
 mod comm;
 mod task;
 mod future;
diff --git a/src/libcore/sys.rs b/src/libcore/sys.rs
index af93009874f..90ea10601ae 100644
--- a/src/libcore/sys.rs
+++ b/src/libcore/sys.rs
@@ -7,7 +7,7 @@ export min_align_of;
 export pref_align_of;
 export refcount;
 export log_str;
-export create_lock, lock_and_signal, condition, methods;
+export lock_and_signal, condition, methods;
 
 enum type_desc = {
     first_param: **libc::c_int,
@@ -126,6 +126,8 @@ impl methods for condition {
 
 #[cfg(test)]
 mod tests {
+    use std;
+    import std::arc;
 
     #[test]
     fn size_of_basic() {
diff --git a/src/libcore/arc.rs b/src/libstd/arc.rs
similarity index 66%
rename from src/libcore/arc.rs
rename to src/libstd/arc.rs
index 312606be906..5200b0fe7a7 100644
--- a/src/libcore/arc.rs
+++ b/src/libstd/arc.rs
@@ -2,12 +2,9 @@
 share immutable data between tasks."]
 
 import comm::{port, chan, methods};
-import sys::methods;
 
 export arc, get, clone, shared_arc, get_arc;
 
-export exclusive, methods;
-
 #[abi = "cdecl"]
 native mod rustrt {
     #[rust_stack]
@@ -19,12 +16,12 @@ native mod rustrt {
         -> libc::intptr_t;
 }
 
-type arc_data<T> = {
+type arc_data<T: const> = {
     mut count: libc::intptr_t,
     data: T
 };
 
-resource arc_destruct<T>(data: *libc::c_void) {
+resource arc_destruct<T: const>(data: *libc::c_void) {
     unsafe {
         let data: ~arc_data<T> = unsafe::reinterpret_cast(data);
         let new_count = rustrt::rust_atomic_decrement(&mut data.count);
@@ -74,43 +71,6 @@ fn clone<T: const>(rc: &arc<T>) -> arc<T> {
     arc_destruct(**rc)
 }
 
-// An arc over mutable data that is protected by a lock.
-type ex_data<T> = {lock: sys::lock_and_signal, data: T};
-type exclusive<T> = arc_destruct<ex_data<T>>;
-
-fn exclusive<T>(-data: T) -> exclusive<T> {
-    let data = ~{mut count: 1, data: {lock: sys::create_lock(),
-                                      data: data}};
-    unsafe {
-        let ptr = unsafe::reinterpret_cast(data);
-        unsafe::forget(data);
-        arc_destruct(ptr)
-    }
-}
-
-impl methods<T> for exclusive<T> {
-    fn clone() -> exclusive<T> {
-        unsafe {
-            // this makes me nervous...
-            let ptr: ~arc_data<ex_data<T>> = unsafe::reinterpret_cast(*self);
-            rustrt::rust_atomic_increment(&mut ptr.count);
-            unsafe::forget(ptr);
-        }
-        arc_destruct(*self)
-    }
-
-    fn with<U>(f: fn(sys::condition, x: &T) -> U) -> U {
-        unsafe {
-            let ptr: ~arc_data<ex_data<T>> = unsafe::reinterpret_cast(*self);
-            let rec: &ex_data<T> = &(*ptr).data;
-            unsafe::forget(ptr);
-            rec.lock.lock_cond() {|c|
-                f(c, &rec.data)
-            }
-        }
-    }
-}
-
 // Convenience code for sharing arcs between tasks
 
 type get_chan<T: const send> = chan<chan<arc<T>>>;
@@ -155,7 +115,6 @@ fn get_arc<T: send const>(c: get_chan<T>) -> arc::arc<T> {
 #[cfg(test)]
 mod tests {
     import comm::*;
-    import future::future;
 
     #[test]
     fn manually_share_arc() {
@@ -201,31 +160,4 @@ mod tests {
 
         assert p.recv() == ();
     }
-
-    #[test]
-    fn exclusive_arc() {
-        let mut futures = [];
-
-        let num_tasks = 10u;
-        let count = 1000u;
-
-        let total = exclusive(~mut 0u);
-
-        for uint::range(0u, num_tasks) {|_i|
-            let total = total.clone();
-            futures += [future::spawn({||
-                for uint::range(0u, count) {|_i|
-                    total.with {|_cond, count|
-                        **count += 1u;
-                    }
-                }
-            })];
-        };
-
-        for futures.each {|f| f.get() };
-
-        total.with {|_cond, total|
-            assert **total == num_tasks * count
-        };
-    }
 }
diff --git a/src/libstd/std.rc b/src/libstd/std.rc
index 2effb04cd3f..10b008d07c8 100644
--- a/src/libstd/std.rc
+++ b/src/libstd/std.rc
@@ -19,7 +19,7 @@ export net, net_tcp;
 export uv, uv_ll, uv_iotask, uv_global_loop;
 export c_vec, util, timer;
 export bitv, deque, fun_treemap, list, map, smallintmap, sort, treemap;
-export rope, arena, par;
+export rope, arena, arc, par;
 export ebml, dbg, getopts, json, rand, sha1, term, time, prettyprint;
 export test, tempfile, serialization;
 export cmp;
@@ -69,6 +69,7 @@ mod term;
 mod time;
 mod prettyprint;
 mod arena;
+mod arc;
 mod par;
 mod cmp;
 
diff --git a/src/test/bench/graph500-bfs.rs b/src/test/bench/graph500-bfs.rs
index e51cb6c98b2..85c77b04c5f 100644
--- a/src/test/bench/graph500-bfs.rs
+++ b/src/test/bench/graph500-bfs.rs
@@ -10,6 +10,7 @@ import std::map;
 import std::map::hashmap;
 import std::deque;
 import std::deque::t;
+import std::arc;
 import std::par;
 import io::writer_util;
 import comm::*;
diff --git a/src/test/compile-fail/no-capture-arc.rs b/src/test/compile-fail/no-capture-arc.rs
index 6c8c80dab0a..6cacd7cd679 100644
--- a/src/test/compile-fail/no-capture-arc.rs
+++ b/src/test/compile-fail/no-capture-arc.rs
@@ -1,5 +1,7 @@
 // error-pattern: copying a noncopyable value
 
+use std;
+import std::arc;
 import comm::*;
 
 fn main() {
diff --git a/src/test/compile-fail/no-reuse-move-arc.rs b/src/test/compile-fail/no-reuse-move-arc.rs
index fa88111d274..34adff6f0ae 100644
--- a/src/test/compile-fail/no-reuse-move-arc.rs
+++ b/src/test/compile-fail/no-reuse-move-arc.rs
@@ -1,3 +1,5 @@
+use std;
+import std::arc;
 import comm::*;
 
 fn main() {
diff --git a/src/test/run-fail/issue-2444.rs b/src/test/run-fail/issue-2444.rs
index 5101de2c46c..1dd1123e7e7 100644
--- a/src/test/run-fail/issue-2444.rs
+++ b/src/test/run-fail/issue-2444.rs
@@ -1,5 +1,8 @@
 // error-pattern:explicit failure
 
+use std;
+import std::arc;
+
 enum e<T: const> { e(arc::arc<T>) }
 
 fn foo() -> e<int> {fail;}