diff --git a/homeassistant/components/script.py b/homeassistant/components/script.py
index 59b55a1289b..1ad07a9a5bd 100644
--- a/homeassistant/components/script.py
+++ b/homeassistant/components/script.py
@@ -15,7 +15,7 @@ from itertools import islice
 import homeassistant.util.dt as date_util
 from homeassistant.const import (
     ATTR_ENTITY_ID, EVENT_TIME_CHANGED, SERVICE_TURN_OFF, SERVICE_TURN_ON,
-    STATE_ON)
+    SERVICE_TOGGLE, STATE_ON)
 from homeassistant.helpers.entity import ToggleEntity, split_entity_id
 from homeassistant.helpers.entity_component import EntityComponent
 from homeassistant.helpers.event import track_point_in_utc_time
@@ -61,6 +61,11 @@ def turn_off(hass, entity_id):
     hass.services.call(DOMAIN, SERVICE_TURN_OFF, {ATTR_ENTITY_ID: entity_id})
 
 
+def toggle(hass, entity_id):
+    """ Toggles script. """
+    hass.services.call(DOMAIN, SERVICE_TOGGLE, {ATTR_ENTITY_ID: entity_id})
+
+
 def setup(hass, config):
     """ Load the scripts from the configuration. """
 
@@ -70,8 +75,12 @@ def setup(hass, config):
         """ Execute a service call to script.<script name>. """
         entity_id = ENTITY_ID_FORMAT.format(service.service)
         script = component.entities.get(entity_id)
-        if script:
-            script.turn_on()
+        if not script:
+            return
+        if script.is_on:
+            _LOGGER.warning("Script %s already running.", entity_id)
+            return
+        script.turn_on()
 
     for object_id, cfg in config[DOMAIN].items():
         if object_id != slugify(object_id):
@@ -99,8 +108,14 @@ def setup(hass, config):
         for script in component.extract_from_service(service):
             script.turn_off()
 
+    def toggle_service(service):
+        """ Toggles a script. """
+        for script in component.extract_from_service(service):
+            script.toggle()
+
     hass.services.register(DOMAIN, SERVICE_TURN_ON, turn_on_service)
     hass.services.register(DOMAIN, SERVICE_TURN_OFF, turn_off_service)
+    hass.services.register(DOMAIN, SERVICE_TOGGLE, toggle_service)
 
     return True
 
diff --git a/tests/components/test_script.py b/tests/components/test_script.py
index 30b7e4e3c8f..9bc1ff57658 100644
--- a/tests/components/test_script.py
+++ b/tests/components/test_script.py
@@ -232,3 +232,73 @@ class TestScript(unittest.TestCase):
         self.assertFalse(script.is_on(self.hass, ENTITY_ID))
 
         self.assertEqual(0, len(calls))
+
+    def test_turn_on_service(self):
+        """
+        Verifies that the turn_on service for a script only turns on scripts
+        that are not currently running.
+        """
+        event = 'test_event'
+        calls = []
+
+        def record_event(event):
+            calls.append(event)
+
+        self.hass.bus.listen(event, record_event)
+
+        self.assertTrue(script.setup(self.hass, {
+            'script': {
+                'test': {
+                    'sequence': [{
+                        'delay': {
+                            'seconds': 5
+                        }
+                    }, {
+                        'event': event,
+                    }]
+                }
+            }
+        }))
+
+        script.turn_on(self.hass, ENTITY_ID)
+        self.hass.pool.block_till_done()
+        self.assertTrue(script.is_on(self.hass, ENTITY_ID))
+        self.assertEqual(0, len(calls))
+
+        # calling turn_on a second time should not advance the script
+        script.turn_on(self.hass, ENTITY_ID)
+        self.hass.pool.block_till_done()
+        self.assertEqual(0, len(calls))
+
+    def test_toggle_service(self):
+        event = 'test_event'
+        calls = []
+
+        def record_event(event):
+            calls.append(event)
+
+        self.hass.bus.listen(event, record_event)
+
+        self.assertTrue(script.setup(self.hass, {
+            'script': {
+                'test': {
+                    'sequence': [{
+                        'delay': {
+                            'seconds': 5
+                        }
+                    }, {
+                        'event': event,
+                    }]
+                }
+            }
+        }))
+
+        script.toggle(self.hass, ENTITY_ID)
+        self.hass.pool.block_till_done()
+        self.assertTrue(script.is_on(self.hass, ENTITY_ID))
+        self.assertEqual(0, len(calls))
+
+        script.toggle(self.hass, ENTITY_ID)
+        self.hass.pool.block_till_done()
+        self.assertFalse(script.is_on(self.hass, ENTITY_ID))
+        self.assertEqual(0, len(calls))