diff --git a/moto/dynamodb2/models.py b/moto/dynamodb2/models.py
index 8e5ecd4b6..5df0c0c28 100644
--- a/moto/dynamodb2/models.py
+++ b/moto/dynamodb2/models.py
@@ -105,6 +105,26 @@ class Item(object):
             "Item": included
         }
 
+    def update(self, update_expression):
+        ACTION_VALUES = ['SET', 'REMOVE']
+
+        action = None
+        for value in update_expression.split():
+            if value in ACTION_VALUES:
+                # An action
+                action = value
+                continue
+            else:
+                # A Real value
+                value = value.lstrip(":").rstrip(",")
+
+            if action == "REMOVE":
+                self.attrs.pop(value, None)
+            elif action == 'SET':
+                key, value = value.split("=:")
+                # TODO deal with other types
+                self.attrs[key] = DynamoType({"S": value})
+
 
 class Table(object):
 
@@ -182,7 +202,7 @@ class Table(object):
     def has_range_key(self):
         return self.range_key_attr is not None
 
-    def get_item(self, hash_key, range_key):
+    def get_item(self, hash_key, range_key=None):
         if self.has_range_key and not range_key:
             raise ValueError("Table has a range key, but no range key was passed into get_item")
         try:
@@ -293,8 +313,11 @@ class DynamoDBBackend(BaseBackend):
         range_key = DynamoType(keys[table.range_key_attr]) if table.has_range_key else None
         return hash_key, range_key
 
+    def get_table(self, table_name):
+        return self.tables.get(table_name)
+
     def get_item(self, table_name, keys):
-        table = self.tables.get(table_name)
+        table = self.get_table(table_name)
         if not table:
             return None
         hash_key, range_key = self.get_keys_value(table, keys)
@@ -322,6 +345,14 @@ class DynamoDBBackend(BaseBackend):
 
         return table.scan(scan_filters)
 
+    def update_item(self, table_name, key, update_expression):
+        table = self.get_table(table_name)
+
+        hash_value = DynamoType(key)
+        item = table.get_item(hash_value)
+        item.update(update_expression)
+        return item
+
     def delete_item(self, table_name, keys):
         table = self.tables.get(table_name)
         if not table:
diff --git a/moto/dynamodb2/responses.py b/moto/dynamodb2/responses.py
index 9d6d31f73..4cc064bf6 100644
--- a/moto/dynamodb2/responses.py
+++ b/moto/dynamodb2/responses.py
@@ -315,3 +315,13 @@ class DynamoHandler(BaseResponse):
         else:
             er = 'com.amazonaws.dynamodb.v20120810#ConditionalCheckFailedException'
             return self.error(er)
+
+    def update_item(self):
+        name = self.body['TableName']
+        key = self.body['Key']
+        update_expression = self.body['UpdateExpression']
+        item = dynamodb_backend2.update_item(name, key, update_expression)
+
+        item_dict = item.to_json()
+        item_dict['ConsumedCapacityUnits'] = 0.5
+        return dynamo_json_dump(item_dict)
diff --git a/tests/test_dynamodb2/test_dynamodb_table_without_range_key.py b/tests/test_dynamodb2/test_dynamodb_table_without_range_key.py
index 15348a24a..9c68b0cd4 100644
--- a/tests/test_dynamodb2/test_dynamodb_table_without_range_key.py
+++ b/tests/test_dynamodb2/test_dynamodb_table_without_range_key.py
@@ -384,3 +384,55 @@ def test_get_special_item():
     table.put_item(data=data)
     returned_item = table.get_item(**{'date-joined': 127549192})
     dict(returned_item).should.equal(data)
+
+
+@mock_dynamodb2
+def test_update_item_remove():
+    conn = boto.dynamodb2.connect_to_region("us-west-2")
+    table = Table.create('messages', schema=[
+        HashKey('username')
+    ])
+
+    data = {
+        'username': "steve",
+        'SentBy': 'User A',
+        'SentTo': 'User B',
+    }
+    table.put_item(data=data)
+    key_map = {
+        "S": "steve"
+    }
+
+    # Then remove the SentBy field
+    conn.update_item("messages", key_map, update_expression="REMOVE :SentBy, :SentTo")
+
+    returned_item = table.get_item(username="steve")
+    dict(returned_item).should.equal({
+        'username': "steve",
+    })
+
+
+@mock_dynamodb2
+def test_update_item_set():
+    conn = boto.dynamodb2.connect_to_region("us-west-2")
+    table = Table.create('messages', schema=[
+        HashKey('username')
+    ])
+
+    data = {
+        'username': "steve",
+        'SentBy': 'User A',
+    }
+    table.put_item(data=data)
+    key_map = {
+        "S": "steve"
+    }
+
+    conn.update_item("messages", key_map, update_expression="SET foo=:bar, blah=:baz REMOVE :SentBy")
+
+    returned_item = table.get_item(username="steve")
+    dict(returned_item).should.equal({
+        'username': "steve",
+        'foo': 'bar',
+        'blah': 'baz',
+    })