diff --git a/synapse/rest/client/v2_alpha/__init__.py b/synapse/rest/client/v2_alpha/__init__.py
index 5831ff0e62..a108132346 100644
--- a/synapse/rest/client/v2_alpha/__init__.py
+++ b/synapse/rest/client/v2_alpha/__init__.py
@@ -22,6 +22,7 @@ from . import (
     receipts,
     keys,
     tokenrefresh,
+    tags,
 )
 
 from synapse.http.server import JsonResource
@@ -44,3 +45,4 @@ class ClientV2AlphaRestResource(JsonResource):
         receipts.register_servlets(hs, client_resource)
         keys.register_servlets(hs, client_resource)
         tokenrefresh.register_servlets(hs, client_resource)
+        tags.register_servlets(hs, client_resource)
diff --git a/synapse/rest/client/v2_alpha/tags.py b/synapse/rest/client/v2_alpha/tags.py
new file mode 100644
index 0000000000..c4a670c5a7
--- /dev/null
+++ b/synapse/rest/client/v2_alpha/tags.py
@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ._base import client_v2_pattern
+
+from synapse.http.servlet import RestServlet
+
+from twisted.internet import defer
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class TagListServlet(RestServlet):
+    """
+    GET /user/{user_id}/rooms/{room_id}/tags HTTP/1.1
+    """
+    PATTERN = client_v2_pattern(
+        "/user/(?P<user_id>[^/]*)/rooms/(?P<room_id>[^/]*)/tags"
+    )
+
+    def __init__(self, hs):
+        super(TagListServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, user_id, room_id):
+        auth_user, _ = yield self.auth.get_user_by_req(request)
+        if user_id != auth_user.to_string():
+            raise AuthError(403, "Cannot get tags for other users.")
+
+        tags = yield self.store.get_tags_for_room(user_id, room_id)
+
+        defer.returnValue((200, {"tags": tags}))
+
+
+class TagServlet(RestServlet):
+    """
+    PUT /user/{user_id}/rooms/{room_id}/tags/{tag} HTTP/1.1
+    DELETE /user/{user_id}/rooms/{room_id}/tags/{tag} HTTP/1.1
+    """
+    PATTERN = client_v2_pattern(
+        "/user/(?P<user_id>[^/]*)/rooms/(?P<room_id>[^/]*)/tags/(?P<tag>[^/]*)"
+    )
+    def __init__(self, hs):
+        super(TagServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, user_id, room_id, tag):
+        auth_user, _ = yield self.auth.get_user_by_req(request)
+        if user_id != auth_user.to_string():
+            raise AuthError(403, "Cannot add tags for other users.")
+
+        yield self.store.add_tag_to_room(user_id, room_id, tag)
+
+        # TODO: poke the notifier.
+        defer.returnValue((200, {}))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, user_id, room_id, tag):
+        auth_user, _ = yield self.auth.get_user_by_req(request)
+        if user_id != auth_user.to_string():
+            raise AuthError(403, "Cannot add tags for other users.")
+
+        yield self.store.remove_tag_from_room(user_id, room_id, tag)
+
+        # TODO: poke the notifier.
+        defer.returnValue((200, {}))
+
+
+def register_servlets(hs, http_server):
+    TagListServlet(hs).register(http_server)
+    TagServlet(hs).register(http_server)
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index a1bd9c4ce9..e7443f2838 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -41,6 +41,7 @@ from .end_to_end_keys import EndToEndKeyStore
 
 from .receipts import ReceiptsStore
 from .search import SearchStore
+from .tags import TagsStore
 
 
 import logging
@@ -71,6 +72,7 @@ class DataStore(RoomMemberStore, RoomStore,
                 ReceiptsStore,
                 EndToEndKeyStore,
                 SearchStore,
+                TagsStore,
                 ):
 
     def __init__(self, hs):
diff --git a/synapse/storage/schema/delta/25/tags.sql b/synapse/storage/schema/delta/25/tags.sql
new file mode 100644
index 0000000000..168766dcf3
--- /dev/null
+++ b/synapse/storage/schema/delta/25/tags.sql
@@ -0,0 +1,37 @@
+/* Copyright 2015 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+CREATE TABLE IF NOT EXISTS room_tags(
+    user_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    tag     TEXT NOT NULL,  -- The name of the tag.
+    CONSTRAINT room_tag_uniqueness UNIQUE (user_id, room_id, tag)
+);
+
+CREATE TABLE IF NOT EXISTS room_tags_revisions (
+    user_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    stream_id BIGINT NOT NULL, -- The current version of the room tags.
+    CONSTRAINT room_tag_revisions_uniqueness UNIQUE (user_id, room_id)
+);
+
+CREATE TABLE IF NOT EXISTS private_user_data_max_stream_id(
+    Lock CHAR(1) NOT NULL DEFAULT 'X' UNIQUE,  -- Makes sure this table only has one row.
+    stream_id  BIGINT NOT NULL,
+    CHECK (Lock='X')
+);
+
+INSERT INTO private_user_data_max_stream_id (stream_id) VALUES (0);
diff --git a/synapse/storage/tags.py b/synapse/storage/tags.py
new file mode 100644
index 0000000000..507e60596f
--- /dev/null
+++ b/synapse/storage/tags.py
@@ -0,0 +1,190 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014, 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ._base import SQLBaseStore
+from synapse.util.caches.descriptors import cached
+from twisted.internet import defer
+from .util.id_generators import StreamIdGenerator
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class TagsStore(SQLBaseStore):
+    def __init__(self, hs):
+        super(TagsStore, self).__init__(hs)
+
+        self._private_user_data_id_gen = StreamIdGenerator(
+            "private_user_data_max_stream_id", "stream_id"
+        )
+
+    @cached()
+    def get_tags_for_user(self, user_id):
+        """Get all the tags for a user.
+
+
+        Args:
+            user_id(str): The user to get the tags for.
+        Returns:
+            A deferred dict mapping from room_id strings to lists of tag
+            strings.
+        """
+
+        deferred = self._simple_select_list(
+            "room_tags", {"user_id": user_id}, ["room_id", "tag"]
+        )
+
+        @deferred.addCallback
+        def tags_by_room(rows):
+            tags_by_room = {}
+            for row in rows:
+                tags_by_room.setdefault(row["room_id"], []).append(row["tag"])
+            return tags_by_room
+
+        return deferred
+
+    @defer.inlineCallbacks
+    def get_updated_tags(self, user_id, stream_id):
+        """Get all the tags for the rooms where the tags have changed since the
+        given version
+
+        Args:
+            user_id(str): The user to get the tags for.
+            stream_id(int): The earliest update to get for the user.
+        Returns:
+            A deferred dict mapping from room_id strings to lists of tag
+            strings for all the rooms that changed since the stream_id token.
+        """
+        def get_updated_tags_txn(txn):
+            sql = (
+                "SELECT room_id from room_tags_revisions"
+                " WHERE user_id = ? AND stream_id > ?"
+            )
+            txn.execute(sql, (user_id, stream_id))
+            room_ids = [row[0] for row in txn.fetchall()]
+            return room_ids
+
+        room_ids = yield self.runInteraction(
+            "get_updated_tags", get_updated_tags_txn
+        )
+
+        results = {}
+        if room_ids:
+            tags_by_room = yield self.get_tags_for_user(self, user_id)
+            for room_id in rooms_ids:
+                results[room_id] = tags_by_room[room_id]
+
+        defer.returnValue(results)
+
+    def get_tags_for_room(self, user_id, room_id):
+        """Get all the tags for the given room
+        Args:
+            user_id(str): The user to get tags for
+            room_id(str): The room to get tags for
+        Returns:
+            A deferred list of string tags.
+        """
+        return self._simple_select_onecol(
+            table="room_tags",
+            keyvalues={"user_id": user_id, "room_id": room_id},
+            retcol="tag",
+            desc="get_tags_for_room",
+        )
+
+    @defer.inlineCallbacks
+    def add_tag_to_room(self, user_id, room_id, tag):
+        """Add a tag to a room for a user.
+        Returns:
+            A deferred that completes once the tag has been added.
+        """
+        def add_tag_txn(txn, next_id):
+            sql = (
+                "INSERT INTO room_tags (user_id, room_id, tag)"
+                " VALUES (?, ?, ?)"
+            )
+            try:
+                txn.execute(sql, (user_id, room_id, tag))
+            except database_engine.module.IntegrityError as e:
+                # Return early if the row is already in the table
+                # and we don't need to bump the revision number of the
+                # private_user_data.
+                return
+            self._update_revision_txn(txn, user_id, room_id, next_id)
+
+        with (yield self._private_user_data_id_gen.get_next(self)) as next_id:
+            yield self.runInteraction("add_tag", add_tag_txn, next_id)
+
+        self.get_tags_for_user.invalidate((user_id,))
+
+    @defer.inlineCallbacks
+    def remove_tag_from_room(self, user_id, room_id, tag):
+        """Remove a tag from a room for a user.
+        Returns:
+            A deffered that completes once the tag has been removed
+        """
+        def remove_tag_txn(txn, next_id):
+            sql = (
+                "DELETE FROM room_tags "
+                " WHERE user_id = ? AND room_id = ? AND tag = ?"
+            )
+            txn.execute(sql, (user_id, room_id, tag))
+            self._update_revision_txn(txn, user_id, room_id, next_id)
+
+        with (yield self._private_user_data_id_gen.get_next(self)) as next_id:
+            yield self.runInteraction("remove_tag", remove_tag_txn, next_id)
+
+        self.get_tags_for_user.invalidate((user_id,))
+
+    def _update_revision_txn(self, txn, user_id, room_id, next_id):
+        """Update the latest revision of the tags for the given user and room.
+
+        Args:
+            txn: The database cursor
+            user_id(str): The ID of the user.
+            room_id(str): The ID of the room.
+            next_id(int): The the revision to advance to.
+        """
+
+        update_max_id_sql = (
+            "UPDATE private_user_data_max_stream_id"
+            " SET stream_id = ?"
+            " WHERE stream_id < ?"
+        )
+        txn.execute(update_max_id_sql, (next_id, next_id))
+
+        update_sql = (
+            "UPDATE room_tags_revisions"
+            " SET stream_id = ?"
+            " WHERE user_id = ?"
+            " AND room_id = ?"
+        )
+        txn.execute(update_sql, (next_id, user_id, room_id))
+
+        if txn.rowcount == 0:
+            insert_sql = (
+                "INSERT INTO room_tags_revisions (user_id, room_id, stream_id)"
+                " VALUES (?, ?, ?)"
+            )
+            try:
+                txn.execute(insert_sql, (user_id, room_id, next_id))
+            except database_engine.module.IntegrityError as e:
+                # Ignore insertion errors. It doesn't matter if the row wasn't
+                # inserted because if two updates happend concurrently the one
+                # with the higher stream_id will not be reported to a client
+                # unless the previous update has completed. It doesn't matter
+                # which stream_id ends up in the table, as long as it is higher
+                # than the id that the client has.
+                pass