diff --git a/tests/test_algorithm.py b/tests/test_algorithm.py
index b19eb601..4c6b1965 100644
--- a/tests/test_algorithm.py
+++ b/tests/test_algorithm.py
@@ -58,7 +58,15 @@ from zipline.errors import (
     UnsupportedDatetimeFormat,
     CannotOrderDelistedAsset,
     SetCancelPolicyPostInit,
-    UnsupportedCancelPolicy
+    UnsupportedCancelPolicy,
+    OrderInBeforeTradingStart)
+from zipline.api import (
+    order,
+    order_value,
+    order_percent,
+    order_target,
+    order_target_value,
+    order_target_percent
 )
 
 from zipline.finance.commission import PerShare
@@ -362,8 +370,8 @@ def handle_data(context, data):
                 self.assertEqual(all_orders[2], orders_2)
                 self.assertEqual(len(all_orders[2]), 3)
 
-                for order in orders_2:
-                    algo.cancel_order(order)
+                for order_ in orders_2:
+                    algo.cancel_order(order_)
 
                 all_orders = algo.get_open_orders()
                 self.assertEqual(all_orders, {})
@@ -759,6 +767,32 @@ class TestTransformAlgorithm(WithLogger,
         )
         algo.run(self.data_portal)
 
+    @parameterized.expand([
+        (order, 1),
+        (order_value, 1000),
+        (order_target, 1),
+        (order_target_value, 1000),
+        (order_percent, 1),
+        (order_target_percent, 1),
+    ])
+    def test_cannot_order_in_before_trading_start(self, order_method, amount):
+        algotext = """
+from zipline.api import sid
+from zipline.api import {order_func}
+
+def initialize(context):
+     context.asset = sid(133)
+
+def before_trading_start(context, data):
+     {order_func}(context.asset, {arg})
+     """.format(order_func=order_method.__name__, arg=amount)
+
+        algo = TradingAlgorithm(script=algotext, sim_params=self.sim_params,
+                                data_frequency='daily', env=self.env)
+
+        with self.assertRaises(OrderInBeforeTradingStart):
+            algo.run(self.data_portal)
+
     def test_run_twice(self):
         algo1 = TestRegisterTransformAlgorithm(
             sim_params=self.sim_params,
diff --git a/zipline/algorithm.py b/zipline/algorithm.py
index dea5c74e..16ef2612 100644
--- a/zipline/algorithm.py
+++ b/zipline/algorithm.py
@@ -51,7 +51,8 @@ from zipline.errors import (
     UnsupportedDatetimeFormat,
     UnsupportedOrderParameters,
     UnsupportedSlippageModel,
-    CannotOrderDelistedAsset, UnsupportedCancelPolicy, SetCancelPolicyPostInit)
+    CannotOrderDelistedAsset, UnsupportedCancelPolicy, SetCancelPolicyPostInit,
+    OrderInBeforeTradingStart)
 from zipline.finance.trading import TradingEnvironment
 from zipline.finance.blotter import Blotter
 from zipline.finance.commission import PerShare, PerTrade, PerDollar
@@ -87,7 +88,7 @@ from zipline.utils.api_support import (
     require_initialized,
     require_not_initialized,
     ZiplineAPI,
-)
+    disallowed_in_before_trading_start)
 from zipline.utils.input_validation import ensure_upper_case
 from zipline.utils.cache import CachedObject, Expired
 import zipline.utils.events
@@ -968,6 +969,7 @@ class TradingAlgorithm(object):
         return True
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order(self, asset, amount,
               limit_price=None,
               stop_price=None,
@@ -1055,6 +1057,7 @@ class TradingAlgorithm(object):
             return MarketOrder()
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order_value(self, asset, value,
                     limit_price=None, stop_price=None, style=None):
         """
@@ -1205,6 +1208,7 @@ class TradingAlgorithm(object):
         self.sim_params.data_frequency = value
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order_percent(self, asset, percent,
                       limit_price=None, stop_price=None, style=None):
         """
@@ -1223,6 +1227,7 @@ class TradingAlgorithm(object):
                                 style=style)
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order_target(self, asset, target,
                      limit_price=None, stop_price=None, style=None):
         """
@@ -1249,6 +1254,7 @@ class TradingAlgorithm(object):
                               style=style)
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order_target_value(self, asset, target,
                            limit_price=None, stop_price=None, style=None):
         """
@@ -1270,6 +1276,7 @@ class TradingAlgorithm(object):
                                  style=style)
 
     @api_method
+    @disallowed_in_before_trading_start(OrderInBeforeTradingStart())
     def order_target_percent(self, asset, target,
                              limit_price=None, stop_price=None, style=None):
         """
diff --git a/zipline/errors.py b/zipline/errors.py
index e809d93f..675c3eac 100644
--- a/zipline/errors.py
+++ b/zipline/errors.py
@@ -263,6 +263,13 @@ class HistoryInInitialize(ZiplineError):
     msg = "history() should only be called in handle_data()"
 
 
+class OrderInBeforeTradingStart(ZiplineError):
+    """
+    Raised when an algorithm calls an order method in before_trading_start.
+    """
+    msg = "Cannot place orders inside before_trading_start."
+
+
 class MultipleSymbolsFound(ZiplineError):
     """
     Raised when a symbol() call contains a symbol that changed over
diff --git a/zipline/utils/api_support.py b/zipline/utils/api_support.py
index 5096fc63..75444460 100644
--- a/zipline/utils/api_support.py
+++ b/zipline/utils/api_support.py
@@ -98,3 +98,25 @@ def require_initialized(exception):
             return method(self, *args, **kwargs)
         return wrapped_method
     return decorator
+
+
+def disallowed_in_before_trading_start(exception):
+    """
+    Decorator for API methods that cannot be called from within
+    TradingAlgorithm.before_trading_start.  `exception` will be raised if the
+    method is called inside `before_trading_start`.
+
+    Usage
+    -----
+    @disallowed_in_before_trading_start(SomeException("Don't do that!"))
+    def method(self):
+        # Do stuff that is not allowed inside before_trading_start.
+    """
+    def decorator(method):
+        @wraps(method)
+        def wrapped_method(self, *args, **kwargs):
+            if self._in_before_trading_start:
+                raise exception
+            return method(self, *args, **kwargs)
+        return wrapped_method
+    return decorator