diff --git a/circle.yml b/circle.yml
index 12efe01c..2a01b19f 100644
--- a/circle.yml
+++ b/circle.yml
@@ -26,6 +26,8 @@ dependencies:
         docker save weaveworks/weave-build >$WEAVE_BUILD;
       fi
   post:
+    - sudo apt-get install bc
+    - pip install requests
     - curl https://sdk.cloud.google.com | bash
     - bin/setup-circleci-secrets "$SECRET_PASSWORD"
     - mkdir -p $(dirname $SRCDIR)
diff --git a/test/run_all.sh b/test/run_all.sh
index 7007925d..4884c81f 100755
--- a/test/run_all.sh
+++ b/test/run_all.sh
@@ -24,20 +24,22 @@ check_test_status() {
 # Overwrite assert.sh _assert_cleanup trap with our own
 trap check_test_status EXIT
 
-# If running on circle, only run the tests for my "shard".
-# CIRCLE_NODE_TOTAL is the total number of shards, and
-# CIRCLE_NODE_INDEX is my index.
-i=0
-TESTS=
-for test in *_test.sh; do
-    if [ -z "$CIRCLECI" ] || [ $(($i % $CIRCLE_NODE_TOTAL)) -eq $CIRCLE_NODE_INDEX ]; then
-          TESTS="$TESTS $test"
-    fi
-    i=$(($i + 1))
-done
+TESTS=*_test.sh
+
+# If running on circle, use the scheduler to work out what tests to run
+if [ -n "$CIRCLECI" ]; then
+    TESTS=$(echo $TESTS | ./sched sched $CIRCLE_BUILD_NUM $CIRCLE_NODE_TOTAL $CIRCLE_NODE_INDEX)
+fi
+
+echo Running $TESTS
 
 for t in $TESTS; do
     echo
     greyly echo "---= Running $t =---"
     . $t
+
+    # Report test runtime when running on circle, to help scheduler
+    if [ -n "$CIRCLECI" ]; then
+        ./sched time $t $(bc -l <<< "$tests_time/1000000000")
+    fi
 done
diff --git a/test/sched b/test/sched
new file mode 100755
index 00000000..4a7c7021
--- /dev/null
+++ b/test/sched
@@ -0,0 +1,38 @@
+#!/usr/bin/python
+import sys, string, json
+import requests
+
+BASE_URL="http://positive-cocoa-90213.appspot.com"
+
+def test_time(test_name, runtime):
+  r = requests.post(BASE_URL + "/record/%s/%f" % (test_name, runtime))
+  print r.text
+  assert r.status_code == 204
+
+def test_sched(test_run, shard_count, shard_id):
+  tests = json.dumps({'tests': string.split(sys.stdin.read())})
+  r = requests.post(BASE_URL + "/schedule/%d/%d/%d" % (test_run, shard_count, shard_id), data=tests)
+  assert r.status_code == 200
+  result = r.json()
+  for test in sorted(result['tests']):
+    print test
+
+def usage():
+  print "%s <cmd> <args..>" % sys.argv[0]
+  print "   time <test name> <run time>"
+  print "   sched <test run> <num shards> <shard id>"
+
+def main():
+  if len(sys.argv) < 4:
+    usage()
+    sys.exit(1)
+
+  if sys.argv[1] == "time":
+    test_time(sys.argv[2], float(sys.argv[3]))
+  elif sys.argv[1] == "sched":
+    test_sched(int(sys.argv[2]), int(sys.argv[3]), int(sys.argv[4]))
+  else:
+    usage()
+
+if __name__ == '__main__':
+  main()
diff --git a/test/scheduler/app.yaml b/test/scheduler/app.yaml
new file mode 100644
index 00000000..09773cb8
--- /dev/null
+++ b/test/scheduler/app.yaml
@@ -0,0 +1,14 @@
+application: positive-cocoa-90213
+version: 1
+runtime: python27
+api_version: 1
+threadsafe: true
+
+handlers:
+- url: .*
+  script: main.app
+
+libraries:
+- name: webapp2
+  version: latest
+
diff --git a/test/scheduler/main.py b/test/scheduler/main.py
new file mode 100644
index 00000000..a2cf113b
--- /dev/null
+++ b/test/scheduler/main.py
@@ -0,0 +1,66 @@
+import operator
+
+import flask
+
+from google.appengine.ext import ndb
+
+app = flask.Flask('scheduler')
+app.debug = True
+
+# We use exponential moving average to record
+# test run times.  Higher alpha discounts historic
+# observations faster.
+alpha = 0.3
+
+class Test(ndb.Model):
+  total_run_time = ndb.FloatProperty(default=0.) # Not total, but a EWMA
+  total_runs = ndb.IntegerProperty(default=0)
+
+class Schedule(ndb.Model):
+  shards = ndb.JsonProperty()
+
+@app.route('/record/<test_name>/<runtime>', methods=['POST'])
+@ndb.transactional
+def record(test_name, runtime):
+  test = Test.get_by_id(test_name)
+  if test is None:
+    test = Test(id=test_name)
+  test.total_run_time = (test.total_run_time * (1-alpha)) + (float(runtime) * alpha)
+  test.total_runs += 1
+  test.put()
+  return ('', 204)
+
+@app.route('/schedule/<int:test_run>/<int:shard_count>/<int:shard>', methods=['POST'])
+def schedule(test_run, shard_count, shard):
+  # read tests from body
+  test_names = flask.request.get_json(force=True)['tests']
+
+  # first see if we have a scedule already
+  schedule_id = "%d-%d" % (test_run, shard_count)
+  schedule = Schedule.get_by_id(schedule_id)
+  if schedule is not None:
+    return flask.json.jsonify(tests=schedule.shards[str(shard)])
+
+  # if not, do simple greedy algorithm
+  test_times = ndb.get_multi(ndb.Key(Test, test_name) for test_name in test_names)
+  def avg(test):
+    if test is not None:
+      return test.total_run_time
+    return 1
+  test_times = [(test_name, avg(test)) for test_name, test in zip(test_names, test_times)]
+  test_times_dict = dict(test_times)
+  test_times.sort(key=operator.itemgetter(1))
+
+  shards = {i: [] for i in xrange(shard_count)}
+  while test_times:
+    test_name, time = test_times.pop()
+
+    # find shortest shard and put it in that
+    s, _ = min(((i, sum(test_times_dict[t] for t in shards[i]))
+      for i in xrange(shard_count)), key=operator.itemgetter(1))
+
+    shards[s].append(test_name)
+
+  # atomically insert or retrieve existing schedule
+  schedule = Schedule.get_or_insert(schedule_id, shards=shards)
+  return flask.json.jsonify(tests=schedule.shards[str(shard)])