diff --git a/tuf/interposition/__init__.py b/tuf/interposition/__init__.py
index db2262a9..00c53e7c 100644
--- a/tuf/interposition/__init__.py
+++ b/tuf/interposition/__init__.py
@@ -172,14 +172,21 @@ def __read_configuration(configuration_handler,
                          parent_repository_directory=None,
                          parent_ssl_certificates_directory=None):
   """
-  A generic function to read a TUF interposition configuration off the disk,
-  and handle it. configuration_handler must be a function which accepts a
-  tuf.interposition.Configuration instance."""
+  A generic function to read TUF interposition configurations off a file, and
+  then handle those configurations with a given function. configuration_handler
+  must be a function which accepts a tuf.interposition.Configuration
+  instance.
+
+  Returns the parsed configurations as a dictionary of configurations indexed
+  by hostnames."""
 
   INVALID_TUF_CONFIGURATION = "Invalid configuration for {network_location}!"
   INVALID_TUF_INTERPOSITION_JSON = "Invalid configuration in {filename}!"
   NO_CONFIGURATIONS = "No configurations found in configuration in {filename}!"
 
+  # Configurations indexed by hostnames.
+  parsed_configurations = {}
+
   try:
     with open(filename) as tuf_interposition_json:
       tuf_interpositions = json.load(tuf_interposition_json)
@@ -197,6 +204,7 @@ def __read_configuration(configuration_handler,
 
             configuration = configuration_parser.parse()
             configuration_handler(configuration)
+            parsed_configurations[configuration.hostname] = configuration
 
           except:
             Logger.exception(INVALID_TUF_CONFIGURATION.format(network_location=network_location))
@@ -206,6 +214,10 @@ def __read_configuration(configuration_handler,
     Logger.exception(INVALID_TUF_INTERPOSITION_JSON.format(filename=filename))
     raise
 
+  else:
+    return parsed_configurations
+
+
 
 
 
@@ -218,8 +230,7 @@ def configure(filename="tuf.interposition.json",
               parent_repository_directory=None,
               parent_ssl_certificates_directory=None):
 
-  """
-  The optional parent_repository_directory parameter is used to specify the
+  """The optional parent_repository_directory parameter is used to specify the
   containing parent directory of the "repository_directory" specified in a
   configuration for *all* network locations, because sometimes the absolute
   location of the "repository_directory" is only known at runtime. If you
@@ -259,20 +270,26 @@ def configure(filename="tuf.interposition.json",
 
   Unless any "url_prefix" begins with "https://", "ssl_certificates" is
   optional; it must specify certificates bundled as PEM (RFC 1422).
-  """
 
-  __read_configuration(__updater_controller.add, filename=filename,
-                       parent_repository_directory=parent_repository_directory,
-                       parent_ssl_certificates_directory=parent_ssl_certificates_directory)
+  Returns the parsed configurations as a dictionary of configurations indexed
+  by hostnames."""
+
+  configurations = \
+    __read_configuration(__updater_controller.add, filename=filename,
+                         parent_repository_directory=parent_repository_directory,
+                         parent_ssl_certificates_directory=parent_ssl_certificates_directory)
+
+  return configurations
 
 
 
 
 
-def deconfigure(filename="tuf.interposition.json"):
-  """Remove TUF interposition for a previously read configuration."""
+def deconfigure(configurations):
+  """Remove TUF interposition for previously read configurations."""
 
-  __read_configuration(__updater_controller.remove, filename=filename)
+  for configuration in configurations.itervalues():
+    __updater_controller.remove(configuration)
 
 
 
@@ -328,3 +345,8 @@ def wrapper(self, *args, **kwargs):
 
 # Build and monkey patch public copies of the urllib and urllib2 modules.
 __monkey_patch()
+
+
+
+
+
diff --git a/tuf/interposition/updater.py b/tuf/interposition/updater.py
index 15a789f7..6c83e964 100644
--- a/tuf/interposition/updater.py
+++ b/tuf/interposition/updater.py
@@ -338,3 +338,8 @@ def remove(self, configuration):
     self.__repository_mirror_hostnames.difference_update(repository_mirror_hostnames)
 
     Logger.info(UPDATER_REMOVED_MESSAGE.format(configuration=configuration))
+
+
+
+
+
diff --git a/tuf/tests/system_tests/util_test_tools.py b/tuf/tests/system_tests/util_test_tools.py
index 1c263068..1e5714c0 100755
--- a/tuf/tests/system_tests/util_test_tools.py
+++ b/tuf/tests/system_tests/util_test_tools.py
@@ -154,6 +154,8 @@ def disable_logging():
 
 PASSWD = 'test'
 version = 1
+# Where we keep TUF configurations, if any, between every iteration.
+tuf_configurations = None
 
 
 def init_repo(tuf=False, port=None):
@@ -196,6 +198,8 @@ def init_repo(tuf=False, port=None):
 
 
 def cleanup(root_repo, server_process=None):
+  global tuf_configurations
+
   if server_process is not None:
     if server_process.returncode is None:
       server_process.kill()
@@ -206,9 +210,9 @@ def cleanup(root_repo, server_process=None):
   keystore.clear_keystore()
 
   # Deconfigure interposition.
-  interpose_json = os.path.join(root_repo, 'tuf.interposition.json')
-  if os.path.exists(interpose_json):
-    tuf.interposition.deconfigure(filename=interpose_json)
+  if tuf_configurations is not None:
+    tuf.interposition.deconfigure(tuf_configurations)
+    tuf_configurations = None
 
   # Removing repository directory.
   try:
@@ -365,7 +369,9 @@ def create_interposition_config(root_repo, url):
        (urllib_tuf replaces urllib module)
        urllib_tuf.urlretrieve(url, filename)
 
-  """ 
+  """
+
+  global tuf_configurations
 
   tuf_repo = os.path.join(root_repo, 'tuf_repo')
   tuf_client = os.path.join(root_repo, 'tuf_client')
@@ -396,7 +402,8 @@ def create_interposition_config(root_repo, url):
   with open(interpose_json, 'wb') as fileobj:
     tuf.util.json.dump(interposition_dict, fileobj)
 
-  tuf.interposition.configure(filename=interpose_json)
+  assert tuf_configurations is None
+  tuf_configurations = tuf.interposition.configure(filename=interpose_json)