diff --git a/lib/matrix.js b/lib/matrix.js
index fbe0bc801..bc7cf8f1f 100644
--- a/lib/matrix.js
+++ b/lib/matrix.js
@@ -57,7 +57,9 @@ module.exports.createClient = function(opts) {
     }
     opts.request = request;
     opts.store = new module.exports.MatrixInMemoryStore();
-    opts.scheduler = new module.exports.MatrixScheduler();
+    opts.scheduler = new module.exports.MatrixScheduler(
+        function() {} // TODO
+    );
     return new module.exports.MatrixClient(opts);
 };
 
diff --git a/lib/scheduler.js b/lib/scheduler.js
index a15c59d0f..da5f3c181 100644
--- a/lib/scheduler.js
+++ b/lib/scheduler.js
@@ -9,18 +9,20 @@ var utils = require("./utils");
 /**
  * Construct a scheduler for Matrix.
  * @constructor
+ * @param {module:scheduler~processFn} processFn Required. The function that can
+ * process events in the queue.
  * @param {module:scheduler~retryAlgorithm} retryAlgorithm Optional. The retry
- * algorithm to use.
+ * algorithm to apply when determining when to try to send an event again.
+ * Defaults to {@link module:scheduler~MatrixScheduler.RETRY_BACKOFF_RATELIMIT}.
  * @param {module:scheduler~queueAlgorithm} queueAlgorithm Optional. The queuing
- * algorithm to use.
- * @prop {module:scheduler~retryAlgorithm} retryAlgorithm The retry algorithm to
- * apply when determining when to try to send an event again. Defaults to
- * {@link module:scheduler~MatrixScheduler.RETRY_BACKOFF_RATELIMIT}.
- * @prop {module:scheduler~queueAlgorithm} queueAlgorithm The queuing algorithm
- * to apply when determining which events should be sent before the given event.
- * Defaults to {@link module:scheduler~MatrixScheduler.QUEUE_MESSAGES}.
+ * algorithm to apply when determining which events should be sent before the
+ * given event. Defaults to {@link module:scheduler~MatrixScheduler.QUEUE_MESSAGES}.
  */
-function MatrixScheduler(retryAlgorithm, queueAlgorithm) {
+function MatrixScheduler(processFn, retryAlgorithm, queueAlgorithm) {
+    if (!utils.isFunction(processFn)) {
+        throw new Error("processFn must be a function.");
+    }
+    this.processFn = processFn;
     this.retryAlgorithm = retryAlgorithm || MatrixScheduler.RETRY_BACKOFF_RATELIMIT;
     this.queueAlgorithm = queueAlgorithm || MatrixScheduler.QUEUE_MESSAGES;
     this._queues = {
@@ -29,7 +31,14 @@ function MatrixScheduler(retryAlgorithm, queueAlgorithm) {
 }
 
 /**
- * Remove the head of the queue.
+ * Makes the scheduler start processing events in the queues if it isn't already.
+ */
+MatrixScheduler.prototype.checkQueuesRunning = function() {
+    // TODO
+};
+
+/**
+ * Remove the head of the queue. Reduces the length of the queue by 1.
  * @param {string} queueName The name of the queue to get the event from.
  * @return {MatrixEvent} The head of the queue or <code>null</code>.
  */
@@ -38,7 +47,7 @@ MatrixScheduler.prototype.removeNextEvent = function(queueName) {
     if (!utils.isArray(queue)) {
         return null;
     }
-    return queue[0];
+    return queue.shift();
 };
 
 /**
@@ -56,16 +65,15 @@ MatrixScheduler.prototype.addEventToQueue = function(queueName, event) {
 /**
  * Queue an event if it is required.
  * @param {MatrixEvent} event The event that may be queued.
- * @return {Promise} A promise which will be resolved when the event is sent, if
- * it has been added to a queue, else <code>null</code>.
+ * @return {boolean} True if the event was queued, else false.
  */
 MatrixScheduler.prototype.queueEvent = function(event) {
     var queueName = this.queueAlgorithm(event);
     if (!queueName) {
-        return null;
+        return false;
     }
     this.addEventToQueue(queueName, event);
-    // TODO: Return a promise
+    return true;
 };
 
 /**
@@ -124,7 +132,7 @@ MatrixScheduler.QUEUE_MESSAGES = function(event) {
  * {@link module:models/event.EventStatus.NOT_SENT} and will not be retried.
  */
 
- /**
+/**
  * The queuing algorithm to apply to events. All queues created are serviced in
  * a FIFO manner. To send the event ASAP, return <code>null</code> which will
  * not put this event in a queue. Events that fail to send that form part of
@@ -137,6 +145,13 @@ MatrixScheduler.QUEUE_MESSAGES = function(event) {
  * the event is not put into a queue and will be sent concurrently.
  */
 
+ /**
+ * The function to invoke to process (send) events in the queue.
+ * @callback processFn
+ * @param {MatrixEvent} event The event to send.
+ * @return {Promise} Resolves to the HTTP response, rejects with an HTTP error.
+ */
+
 /**
  * The MatrixScheduler class.
  */