diff --git a/lib/api/routes.js b/lib/api/routes.js
index f2bdc31..bdc91fe 100644
--- a/lib/api/routes.js
+++ b/lib/api/routes.js
@@ -60,9 +60,8 @@ router.get("/commands", function(req, res) {
 });
 
 router.post("/commands/:command", function(req, res) {
-  var command = req.params.command;
-  var result = Cylon.commands[command].apply(Cylon, req.commandParams);
-  res.json({ result: result });
+  var command = Cylon.commands[req.params.command];
+  router.runCommand(req, res, Cylon, command);
 });
 
 router.get("/robots", function(req, res) {
@@ -79,8 +78,7 @@ router.get("/robots/:robot/commands", load, function(req, res) {
 
 router.all("/robots/:robot/commands/:command", load, function(req, res) {
   var command = req.robot.commands[req.params.command];
-  var result = command.apply(req.robot, req.commandParams);
-  res.json({ result: result });
+  router.runCommand(req, res, req.robot, command);
 });
 
 router.get("/robots/:robot/devices", load, function(req, res) {
@@ -117,8 +115,7 @@ router.get("/robots/:robot/devices/:device/commands", load, function(req, res) {
 
 router.all("/robots/:robot/devices/:device/commands/:command", load, function(req, res) {
   var command = req.device.commands[req.params.command];
-  var result = command.apply(req.device, req.commandParams);
-  res.json({ result: result });
+  router.runCommand(req, res, req.device, command);
 });
 
 router.get("/robots/:robot/connections", load, function(req, res) {
@@ -128,3 +125,17 @@ router.get("/robots/:robot/connections", load, function(req, res) {
 router.get("/robots/:robot/connections/:connection", load, function(req, res) {
   res.json({ connection: req.connection });
 });
+
+// Run an MCP, Robot, or Device command.  Process the results immediately,
+// or asynchronously if the result is a Promise.
+router.runCommand = function(req, res, my, command) {
+  var result = command.apply(my, req.commandParams);
+  if (typeof result.then === "function") {
+    result
+      .then(function(result) {return res.json({result: result});})
+      .catch(function(err) {return res.status(500).json({error: err});});
+  }
+  else {
+    res.json({ result: result });
+  }
+};
diff --git a/spec/lib/api/routes.spec.js b/spec/lib/api/routes.spec.js
index 641fb00..7d44dc3 100644
--- a/spec/lib/api/routes.spec.js
+++ b/spec/lib/api/routes.spec.js
@@ -21,6 +21,33 @@ function findFinalHandler(path) {
   return handlers[handlers.length - 1];
 }
 
+function MockPromise() {
+  var my = this;
+  my.resolve = function() {
+    var args = arguments;
+    process.nextTick(function() {
+      my.thenCallback.apply(null, args);
+    });
+    return my;
+  };
+  my.reject = function() {
+    var args = arguments;
+    process.nextTick(function() {
+      my.errorCallback.apply(null, args);
+    });
+    return my;
+  };
+  my.then = function(thenCallback) {
+    my.thenCallback = thenCallback;
+    return my;
+  };
+  my.catch = function(errorCallback) {
+    my.errorCallback = errorCallback;
+    return my;
+  };
+  my.deferred = my;
+}
+
 describe("API routes", function() {
   var routes = [
     ["GET",  "/"],
@@ -55,18 +82,40 @@ describe("API commands", function() {
   var req, res;
   beforeEach(function() {
     Cylon.commands.ping = function() { return "pong"; };
+    Cylon.commands.pingAsync = function() {
+      var promise = new MockPromise();
+      return promise.resolve("immediate pong");
+    };
     req = new MockRequest();
     res = new MockResponse();
+    res.status = function(statusCode) {
+      res.statusCode = statusCode;
+      return res;
+    };
     req.device = {
       name: "testDevice",
       commands: {
-        announce: function(){return "im here";}
+        announce: function(){return "im here";},
+        announceAsync: function() {
+          var promise = new MockPromise();
+          process.nextTick(function(){
+            return promise.reject("sorry, sore throat");
+          });
+          return promise.deferred;
+        }
       }
     };
     req.robot = {
       name: "fred",
       commands: {
-        speak: function(){return "ahem";}
+        speak: function(){return "ahem";},
+        speakAsync: function() {
+          var promise = new MockPromise();
+          process.nextTick(function(){
+            return promise.resolve("see ya in another cycle");
+          });
+          return promise.deferred;
+        }
       },
       devices: {
         testDevice: req.device
@@ -75,12 +124,13 @@ describe("API commands", function() {
   });
   afterEach(function() {
     delete Cylon.commands.ping;
+    delete Cylon.commands.pingAsync;
   });
 
   it("returns the list of MCP commands", function() {
     res.json = function(obj){
       expect(obj.commands).to.exist();
-      expect(obj.commands.length).to.equal(1);
+      expect(obj.commands.length).to.equal(2);
       expect(obj.commands[0]).to.equal("ping");
     };
     findFinalHandler("/commands")(req, res);
@@ -94,11 +144,19 @@ describe("API commands", function() {
     findFinalHandler("/commands/ping")(req, res);
   });
 
+  it("returns an immediate MCP async command", function() {
+    req.params = {command:"pingAsync"};
+    res.json = function(obj){
+      expect(obj.result).to.equal("immediate pong");
+    };
+    findFinalHandler("/commands/pingAsync")(req, res);
+  });
+
   it("returns the list of robot commands", function() {
     req.params = {robot: "fred"};
     res.json = function(obj){
       expect(obj.commands).to.exist();
-      expect(obj.commands.length).to.equal(1);
+      expect(obj.commands.length).to.equal(2);
       expect(obj.commands[0]).to.equal("speak");
     };
     findFinalHandler("/robots/fred/commands")(req, res);
@@ -112,11 +170,19 @@ describe("API commands", function() {
     findFinalHandler("/robots/fred/commands/speak")(req, res);
   });
 
+  it("invokes an asynchronous robot command", function() {
+    req.params = {robot: "fred", command:"speakAsync"};
+    res.json = function(obj){
+      expect(obj.result).to.equal("see ya in another cycle");
+    };
+    findFinalHandler("/robots/fred/commands/speakAsync")(req, res);
+  });
+
   it("returns the list of device commands", function() {
     req.params = {robot: "fred", device: "testDevice" };
     res.json = function(obj){
       expect(obj.commands).to.exist();
-      expect(obj.commands.length).to.equal(1);
+      expect(obj.commands.length).to.equal(2);
       expect(obj.commands[0]).to.equal("announce");
     };
     var path = "/robots/fred/devices/testDevice/commands";
@@ -128,7 +194,17 @@ describe("API commands", function() {
     res.json = function(obj){
       expect(obj.result).to.equal("im here");
     };
-    var path = "/robots/fred/devices/testDevice/commands/speak";
+    var path = "/robots/fred/devices/testDevice/commands/announce";
+    findFinalHandler(path)(req, res);
+  });
+
+  it("returns correctly for an async device command that errored", function() {
+    req.params = {robot: "fred", device: "testDevice", command:"announceAsync"};
+    res.json = function(obj){
+      expect(obj.error).to.equal("sorry, sore throat");
+      expect(res.statusCode).to.equal(500);
+    };
+    var path = "/robots/fred/devices/testDevice/commands/announceAsync";
     findFinalHandler(path)(req, res);
   });