diff --git a/heap.ml b/heap.ml
new file mode 100644
index 00000000..1c6dd28a
--- /dev/null
+++ b/heap.ml
@@ -0,0 +1,75 @@
+(*
+Copyright (c) 2013, Simon Cruanes
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  Redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Binary heaps} *)
+
+type 'a t = {
+  tree: 'a tree;
+  lt: 'a -> 'a -> bool;
+} (** A heap containing values of type 'a *)
+and 'a tree =
+  | Empty
+  | Node of int * 'a tree * 'a * 'a tree
+  (** The complete binary tree (int is max depth) *)
+
+(** Create an empty heap *)
+let empty ~lt =
+  { tree = Empty;
+    lt;
+  }
+
+(** Insert a value in the heap *)
+let insert heap x =
+  let rec insert tree x =
+    match tree with
+    | Empty -> Node (1, Empty, x, Empty)
+    | Node (d, l, y, r) -> failwith "TODO"
+  in
+  { heap with tree = insert heap.tree x }
+
+(** Check whether the heap is empty *)
+let is_empty heap =
+  match heap.tree with
+  | Empty -> true
+  | _ -> false
+
+(** Access the minimal value of the heap, or raises Empty *)
+let min heap =
+  match heap.tree with
+  | Node (_, _, x, _) -> x
+  | Empty -> raise (Invalid_argument "Heap.min on empty heap")
+
+(** Discard the minimal element *)
+let junk heap = failwith "TODO: Heap.junk"
+
+(** Iterate on the elements, in an unspecified order *)
+let iter heap k =
+  let rec iter tree = match tree with
+  | Empty -> ()
+  | Node (_, l, x, r) ->
+    iter l;
+    k x;
+    iter r
+  in iter heap.tree
diff --git a/heap.mli b/heap.mli
new file mode 100644
index 00000000..36a10730
--- /dev/null
+++ b/heap.mli
@@ -0,0 +1,47 @@
+(*
+Copyright (c) 2013, Simon Cruanes
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  Redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Binary heaps} *)
+
+type 'a t
+  (** A heap containing values of type 'a *)
+
+val empty : lt:('a -> 'a -> bool) -> 'a t
+  (** Create an empty heap *)
+
+val insert : 'a t -> 'a -> 'a t
+  (** Insert a value in the heap *)
+
+val is_empty : 'a t -> bool
+  (** Check whether the heap is empty *)
+
+val min : 'a t -> 'a
+  (** Access the minimal value of the heap, or raises Invalid_argument *)
+
+val junk : 'a t -> 'a t
+  (** Discard the minimal element *)
+
+val iter : 'a t -> ('a -> unit) -> unit
+  (** Iterate on the elements, in an unspecified order *)
diff --git a/tests/test_heap.ml b/tests/test_heap.ml
new file mode 100644
index 00000000..1cfa7d4c
--- /dev/null
+++ b/tests/test_heap.ml
@@ -0,0 +1,12 @@
+(** Test heaps *)
+
+open OUnit
+
+let test_empty () =
+  let h = Heap.empty ~lt:(fun x y -> x < y) in
+  OUnit.assert_bool "is_empty empty" (Heap.is_empty h)
+
+let suite =
+  "test_heaps" >:::
+    [ "test_empty" >:: test_empty;
+    ]
diff --git a/tests/tests.ml b/tests/tests.ml
index 62d7d57a..09e6a200 100644
--- a/tests/tests.ml
+++ b/tests/tests.ml
@@ -5,6 +5,7 @@ open OUnit
 let suite =
   "all_tests" >:::
     [ Test_pHashtbl.suite;
+      Test_heap.suite;
     ]
 
 let _ =