diff --git a/IPython/parallel/client/client.py b/IPython/parallel/client/client.py
index 4571023..0df5c7c 100644
--- a/IPython/parallel/client/client.py
+++ b/IPython/parallel/client/client.py
@@ -229,6 +229,13 @@ class Client(HasTraits):
         The name of the Cluster profile to be used to find connector information.
         If run from an IPython application, the default profile will be the same
         as the running application, otherwise it will be 'default'.
+    cluster_id : str
+        String id to added to runtime files, to prevent name collisions when using
+        multiple clusters with a single profile simultaneously.
+        When set, will look for files named like: 'ipcontroller-<cluster_id>-client.json'
+        Since this is text inserted into filenames, typical recommendations apply:
+        Simple character strings are ideal, and spaces are not recommended (but
+        should generally work)
     context : zmq.Context
         Pass an existing zmq.Context instance, otherwise the client will create its own.
     debug : bool
@@ -366,7 +373,7 @@ class Client(HasTraits):
     def __init__(self, url_file=None, profile=None, profile_dir=None, ipython_dir=None,
             context=None, debug=False,
             sshserver=None, sshkey=None, password=None, paramiko=None,
-            timeout=10, **extra_args
+            timeout=10, cluster_id=None, **extra_args
             ):
         if profile:
             super(Client, self).__init__(debug=debug, profile=profile)
@@ -388,7 +395,11 @@ class Client(HasTraits):
         
         if self._cd is not None:
             if url_file is None:
-                url_file = pjoin(self._cd.security_dir, 'ipcontroller-client.json')
+                if cluster_id is None:
+                    client_json = 'ipcontroller-client.json'
+                else:
+                    client_json = 'ipcontroller-%s-client.json' % cluster_id
+                url_or_file = pjoin(self._cd.security_dir, client_json)
         if url_file is None:
             raise ValueError(
                 "I can't find enough information to connect to a hub!"