diff --git a/pymongo/common.py b/pymongo/common.py
index bf5919d84..bff0d7540 100644
--- a/pymongo/common.py
+++ b/pymongo/common.py
@@ -98,12 +98,22 @@ def validate_integer(option, value):
 
 
 def validate_positive_integer(option, value):
-    """Validate that 'value' is a positive integer.
+    """Validate that 'value' is a positive integer, which does not include 0.
+    """
+    val = validate_integer(option, value)
+    if val <= 0:
+        raise ConfigurationError("The value of %s must be "
+                                 "a positive integer" % (option,))
+    return val
+
+
+def validate_non_negative_integer(option, value):
+    """Validate that 'value' is a positive integer or 0.
     """
     val = validate_integer(option, value)
     if val < 0:
         raise ConfigurationError("The value of %s must be "
-                                 "a positive integer" % (option,))
+                                 "a non negative integer" % (option,))
     return val
 
 
@@ -138,6 +148,14 @@ def validate_cert_reqs(option, value):
                                  % (option,))
 
 
+def validate_non_negative_integer_or_none(option, value):
+    """Validate that 'value' is a positive integer or 0 or None.
+    """
+    if value is None:
+        return value
+    return validate_non_negative_integer(option, value)
+
+
 def validate_positive_integer_or_none(option, value):
     """Validate that 'value' is a positive integer or None.
     """
@@ -316,7 +334,7 @@ VALIDATORS = {
     'connecttimeoutms': validate_timeout_or_none,
     'sockettimeoutms': validate_timeout_or_none,
     'waitqueuetimeoutms': validate_timeout_or_none,
-    'waitqueuemultiple': validate_positive_integer_or_none,
+    'waitqueuemultiple': validate_non_negative_integer_or_none,
     'ssl': validate_boolean,
     'ssl_keyfile': validate_readable,
     'ssl_certfile': validate_readable,
diff --git a/pymongo/mongo_client.py b/pymongo/mongo_client.py
index 41b3a8004..8f47d4c94 100644
--- a/pymongo/mongo_client.py
+++ b/pymongo/mongo_client.py
@@ -130,7 +130,7 @@ class MongoClient(common.BaseObject):
           - `max_pool_size` (optional): The maximum number of connections
             that the pool will open simultaneously. If this is set, operations
             will block if there are `max_pool_size` outstanding connections
-            from the pool. Defaults to 100.
+            from the pool. Defaults to 100. Cannot be 0.
           - `document_class` (optional): default class to use for
             documents returned from queries on this client
           - `tz_aware` (optional): if ``True``,
@@ -316,8 +316,8 @@ class MongoClient(common.BaseObject):
 
         self.__max_pool_size = options.get(
             'maxpoolsize',
-            common.validate_positive_integer_or_none('max_pool_size',
-                                                     max_pool_size))
+            common.validate_positive_integer_or_none(
+                'max_pool_size', max_pool_size))
 
         self.__cursor_manager = CursorManager(self)
 
diff --git a/pymongo/mongo_replica_set_client.py b/pymongo/mongo_replica_set_client.py
index 32be49edd..5ba7ef497 100644
--- a/pymongo/mongo_replica_set_client.py
+++ b/pymongo/mongo_replica_set_client.py
@@ -471,7 +471,7 @@ class MongoReplicaSetClient(common.BaseObject):
           - `max_pool_size` (optional): The maximum number of connections
             each pool will open simultaneously. If this is set, operations
             will block if there are `max_pool_size` outstanding connections
-            from the pool. Defaults to 100.
+            from the pool. Defaults to 100. Cannot be 0.
           - `document_class` (optional): default class to use for
             documents returned from queries on this client
           - `tz_aware` (optional): if ``True``,
@@ -635,8 +635,8 @@ class MongoReplicaSetClient(common.BaseObject):
 
         self.__max_pool_size = self.__opts.get(
             'maxpoolsize',
-            common.validate_positive_integer_or_none('max_pool_size',
-                                                     max_pool_size))
+            common.validate_positive_integer_or_none(
+                'max_pool_size', max_pool_size))
 
         common.validate_boolean('tz_aware', tz_aware)
         uuid_representation = options.pop('uuidrepresentation', PYTHON_LEGACY)
diff --git a/test/test_client.py b/test/test_client.py
index 2f4f2fe2a..69089059e 100644
--- a/test/test_client.py
+++ b/test/test_client.py
@@ -106,6 +106,9 @@ class TestClient(unittest.TestCase, TestRequestMixin):
 
         self.assertRaises(ConfigurationError, MongoClient, [])
 
+    def test_max_pool_size_zero(self):
+        self.assertRaises(ConfigurationError, MongoClient, maxPoolSize=0)
+
     def test_constants(self):
         MongoClient.HOST = host
         MongoClient.PORT = port
diff --git a/test/test_replica_set_client.py b/test/test_replica_set_client.py
index cb63fd78e..a3f07b9e5 100644
--- a/test/test_replica_set_client.py
+++ b/test/test_replica_set_client.py
@@ -165,6 +165,10 @@ class TestReplicaSetClient(TestReplicaSetClientBase, TestRequestMixin):
         self.assertEqual(None, client._MongoReplicaSetClient__ssl_certfile)
         self.assertEqual(None, client._MongoReplicaSetClient__ssl_ca_certs)
 
+    def test_repl_max_pool_size_zero(self):
+        self.assertRaises(ConfigurationError, MongoReplicaSetClient,
+                          maxPoolSize=0)
+
     def test_init_disconnected(self):
         c = self._get_client(_connect=False)