diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py
index 54c42d1b9..3cedd479a 100644
--- a/synapse/appservice/scheduler.py
+++ b/synapse/appservice/scheduler.py
@@ -83,7 +83,6 @@ class AppServiceScheduler(object):
             self.clock, self.store, self.as_api, self.txn_ctrl.on_recovered
         )
         self.txn_ctrl.add_recoverers(recoverers)
-        self.txn_ctrl.start_polling()
 
     def submit_event_for_as(self, service, event):
         self.queuer.enqueue(service, event)
@@ -96,24 +95,37 @@ class _ServiceQueuer(object):
     """
 
     def __init__(self, txn_ctrl):
-        self.groups = {}  # dict of {service: [events]}
+        self.queued_events = {}  # dict of {service_id: [events]}
+        self.pending_requests = {}  # dict of {service_id: Deferred}
         self.txn_ctrl = txn_ctrl
 
     def enqueue(self, service, event):
-        # if nothing in queue for this service, send event immediately and add
-        # callbacks.
-        self.txn_ctrl.send(service, [event])
+        # if this service isn't being sent something
+        if not self.pending_requests.get(service.id):
+            self._send_request(service, [event])
+        else:
+            # add to queue for this service
+            if service.id not in self.queued_events:
+                self.queued_events[service.id] = []
+            self.queued_events[service.id].append(event)
 
-        # else add to queue for this service
+    def _send_request(self, service, events):
+        # send request and add callbacks
+        d = self.txn_ctrl.send(service, events)
+        d.addCallback(self._on_request_finish)
+        d.addErrback(self._on_request_fail)
+        self.pending_requests[service.id] = d
 
-        if service not in self.groups:
-            self.groups[service] = []
-        self.groups[service].append(event)
+    def _on_request_finish(self, service):
+        self.pending_requests[service.id] = None
+        # if there are queued events, then send them.
+        if (service.id in self.queued_events
+                and len(self.queued_events[service.id]) > 0):
+            self._send_request(service, self.queued_events[service.id])
+            self.queued_events[service.id] = []
 
-    def drain_groups(self):
-        groups = self.groups
-        self.groups = {}
-        return groups
+    def _on_request_fail(self, err):
+        logger.error("AS request failed: %s", err)
 
 
 class _TransactionController(object):
@@ -142,6 +154,8 @@ class _TransactionController(object):
                     self._start_recoverer(service)
         except Exception as e:
             logger.exception(e)
+        # request has finished
+        defer.returnValue(service)
 
     @defer.inlineCallbacks
     def on_recovered(self, recoverer):
diff --git a/tests/appservice/test_scheduler.py b/tests/appservice/test_scheduler.py
index 38d792eb0..82a596509 100644
--- a/tests/appservice/test_scheduler.py
+++ b/tests/appservice/test_scheduler.py
@@ -197,16 +197,56 @@ class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
 
     def test_send_single_event_no_queue(self):
         # Expect the event to be sent immediately.
-        pass
+        service = Mock(id=4)
+        event = Mock()
+        self.queuer.enqueue(service, event)
+        self.txn_ctrl.send.assert_called_once_with(service, [event])
 
     def test_send_single_event_with_queue(self):
-        # - Send an event and don't resolve it just yet.
-        # - Send another event: expect send() to NOT be called.
-        # - Resolve the send event
-        # - Expect queued event to be sent
-        pass
+        d = defer.Deferred()
+        self.txn_ctrl.send = Mock(return_value=d)
+        service = Mock(id=4)
+        event = Mock(event_id="first")
+        event2 = Mock(event_id="second")
+        event3 = Mock(event_id="third")
+        # Send an event and don't resolve it just yet.
+        self.queuer.enqueue(service, event)
+        # Send more events: expect send() to NOT be called multiple times.
+        self.queuer.enqueue(service, event2)
+        self.queuer.enqueue(service, event3)
+        self.txn_ctrl.send.assert_called_with(service, [event])
+        self.assertEquals(1, self.txn_ctrl.send.call_count)
+        # Resolve the send event: expect the queued events to be sent
+        d.callback(service)
+        self.txn_ctrl.send.assert_called_with(service, [event2, event3])
+        self.assertEquals(2, self.txn_ctrl.send.call_count)
 
     def test_multiple_service_queues(self):
         # Tests that each service has its own queue, and that they don't block
         # on each other.
-        pass
+        srv1 = Mock(id=4)
+        srv_1_defer = defer.Deferred()
+        srv_1_event = Mock(event_id="srv1a")
+        srv_1_event2 = Mock(event_id="srv1b")
+
+        srv2 = Mock(id=6)
+        srv_2_defer = defer.Deferred()
+        srv_2_event = Mock(event_id="srv2a")
+        srv_2_event2 = Mock(event_id="srv2b")
+
+        send_return_list = [srv_1_defer, srv_2_defer]
+        self.txn_ctrl.send = Mock(side_effect=lambda x,y: send_return_list.pop(0))
+
+        # send events for different ASes and make sure they are sent
+        self.queuer.enqueue(srv1, srv_1_event)
+        self.queuer.enqueue(srv1, srv_1_event2)
+        self.txn_ctrl.send.assert_called_with(srv1, [srv_1_event])
+        self.queuer.enqueue(srv2, srv_2_event)
+        self.queuer.enqueue(srv2, srv_2_event2)
+        self.txn_ctrl.send.assert_called_with(srv2, [srv_2_event])
+
+        # make sure callbacks for a service only send queued events for THAT
+        # service
+        srv_2_defer.callback(srv2)
+        self.txn_ctrl.send.assert_called_with(srv2, [srv_2_event2])
+        self.assertEquals(3, self.txn_ctrl.send.call_count)