diff --git a/README.rst b/README.rst
index 327a703..13c82a1 100644
--- a/README.rst
+++ b/README.rst
@@ -36,6 +36,36 @@ If you would like to delete a password stored in your system keyring, you can cl
 
 >>> icloud --username=jappleseed@apple.com --delete-from-keyring
 
+*******************************
+Two-factor authentication (2FA)
+*******************************
+
+If you have enabled two-factor authentication for the account you will have to do some extra work:
+
+.. code-block:: python
+
+	if icloud.requires_2fa:
+	    print "Two-factor authentication required. Your trusted devices are:"
+
+	    devices = icloud.trusted_devices
+	    for i, device in enumerate(devices):
+	        print "  %s: %s" % (i, device.get('deviceName',
+	            "SMS to %s" % device.get('phoneNumber')))
+
+	    device = click.prompt('Which device would you like to use?', default=0)
+	    device = devices[device]
+	    if not icloud.send_verification_code(device):
+	        print "Failed to send verification code"
+	        sys.exit(1)
+
+	    code = click.prompt('Please enter validation code')
+	    if not icloud.validate_verification_code(device, code):
+	        print "Failed to verify verification code"
+	        sys.exit(1)
+
+Note: Both regular login and two-factor authentication will expire after an interval set by Apple, at which point you will have to re-authenticate. This interval is currently two months.
+>>>>>>> Add support for two-factor authentication
+
 =======
 Devices
 =======
diff --git a/pyicloud/base.py b/pyicloud/base.py
index 2630ef7..8bf1e5c 100644
--- a/pyicloud/base.py
+++ b/pyicloud/base.py
@@ -12,7 +12,8 @@ from re import match
 
 from pyicloud.exceptions import (
     PyiCloudFailedLoginException,
-    PyiCloudAPIResponseError
+    PyiCloudAPIResponseError,
+    PyiCloud2FARequiredError
 )
 from pyicloud.services import (
     FindMyiPhoneServiceManager,
@@ -46,7 +47,8 @@ class PyiCloudPasswordFilter(logging.Filter):
 
 
 class PyiCloudSession(requests.Session):
-    def __init__(self):
+    def __init__(self, service):
+        self.service = service
         super(PyiCloudSession, self).__init__()
 
     def request(self, *args, **kwargs):
@@ -76,6 +78,10 @@ class PyiCloudSession(requests.Session):
         code = json.get('errorCode')
 
         if reason:
+            if self.service.requires_2fa and \
+                    reason == 'Missing X-APPLE-WEBAUTH-TOKEN cookie':
+                raise PyiCloud2FARequiredError(response.url)
+
             api_error = PyiCloudAPIResponseError(reason, code)
             logger.error(api_error)
             raise api_error
@@ -99,7 +105,7 @@ class PyiCloudService(object):
         if password is None:
             password = get_password_from_keyring(apple_id)
 
-        self.discovery = None
+        self.data = {}
         self.client_id = str(uuid.uuid1()).upper()
         self.user = {'apple_id': apple_id, 'password': password}
         logger.addFilter(PyiCloudPasswordFilter(password))
@@ -119,7 +125,7 @@ class PyiCloudService(object):
                 'pyicloud',
             )
 
-        self.session = PyiCloudSession()
+        self.session = PyiCloudSession(self)
         self.session.verify = verify
         self.session.headers.update({
             'Origin': self._home_endpoint,
@@ -173,8 +179,8 @@ class PyiCloudService(object):
             os.mkdir(self._cookie_directory)
         self.session.cookies.save()
 
-        self.discovery = resp
-        self.webservices = self.discovery['webservices']
+        self.data = resp
+        self.webservices = self.data['webservices']
 
         logger.info("Authentication completed successfully")
         logger.debug(self.params)
@@ -186,6 +192,56 @@ class PyiCloudService(object):
             ''.join([c for c in self.user.get('apple_id') if match(r'\w', c)])
         )
 
+    @property
+    def requires_2fa(self):
+        """ Returns True if two-factor authentication is required."""
+        return self.data.get('hsaChallengeRequired', False)
+
+    @property
+    def trusted_devices(self):
+        """ Returns devices trusted for two-factor authentication."""
+        request = self.session.get(
+            '%s/listDevices' % self._setup_endpoint,
+            params=self.params
+        )
+        return request.json().get('devices')
+
+    def send_verification_code(self, device):
+        """ Requests that a verification code is sent to the given device"""
+        data = json.dumps(device)
+        request = self.session.post(
+            '%s/sendVerificationCode' % self._setup_endpoint,
+            params=self.params,
+            data=data
+        )
+        return request.json().get('success', False)
+
+    def validate_verification_code(self, device, code):
+        """ Verifies a verification code received on a two-factor device"""
+        device.update({
+            'verificationCode': code,
+            'trustBrowser': True
+        })
+        data = json.dumps(device)
+
+        try:
+            request = self.session.post(
+                '%s/validateVerificationCode' % self._setup_endpoint,
+                params=self.params,
+                data=data
+            )
+        except PyiCloudAPIResponseError, error:
+            if error.code == -21669:
+                # Wrong verification code
+                return False
+            raise
+
+        # Re-authenticate, which will both update the 2FA data, and
+        # ensure that we save the X-APPLE-WEBAUTH-HSA-TRUST cookie.
+        self.authenticate()
+
+        return not self.requires_2fa
+
     @property
     def devices(self):
         """ Return all devices."""
diff --git a/pyicloud/exceptions.py b/pyicloud/exceptions.py
index 098b344..487def4 100644
--- a/pyicloud/exceptions.py
+++ b/pyicloud/exceptions.py
@@ -22,5 +22,15 @@ class PyiCloudFailedLoginException(PyiCloudException):
     pass
 
 
+class PyiCloud2FARequiredError(PyiCloudException):
+    def __init__(self, url):
+        message = "Two-factor authentication required for %s" % url
+        super(PyiCloud2FARequiredError, self).__init__(message)
+
+
+class PyiCloudNoDevicesException(Exception):
+    pass
+
+
 class NoStoredPasswordAvailable(PyiCloudException):
     pass