diff --git a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/descriptor.proto b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/descriptor.proto
index a785f79..031433e 100644
--- a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/descriptor.proto
+++ b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/descriptor.proto
@@ -228,7 +228,7 @@
 // * For options which will be published and used publicly by multiple
 //   independent entities, e-mail protobuf-global-extension-registry@google.com
 //   to reserve extension numbers. Simply provide your project name (e.g.
-//   Object-C plugin) and your porject website (if available) -- there's no need
+//   Object-C plugin) and your project website (if available) -- there's no need
 //   to explain how you intend to use them. Usually you only need one extension
 //   number. You can declare multiple options with only one extension number by
 //   putting them in a sub-message. See the Custom Options section of the docs
diff --git a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_custom_options.proto b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_custom_options.proto
index e591d29..2f4e3fd 100644
--- a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_custom_options.proto
+++ b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_custom_options.proto
@@ -321,7 +321,7 @@
 }
 
 // Allow Aggregate to be used as an option at all possible locations
-// in the .proto grammer.
+// in the .proto grammar.
 extend google.protobuf.FileOptions      { optional Aggregate fileopt    = 15478479; }
 extend google.protobuf.MessageOptions   { optional Aggregate msgopt     = 15480088; }
 extend google.protobuf.FieldOptions     { optional Aggregate fieldopt   = 15481374; }
diff --git a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_import.proto b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_import.proto
index c115b11..ec36cca 100644
--- a/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_import.proto
+++ b/python/compatibility_tests/v2.5.0/protos/src/proto/google/protobuf/unittest_import.proto
@@ -43,7 +43,7 @@
 
 option optimize_for = SPEED;
 
-// Excercise the java_package option.
+// Exercise the java_package option.
 option java_package = "com.google.protobuf.test";
 
 // Do not set a java_outer_classname here to verify that Proto2 works without
diff --git a/python/compatibility_tests/v2.5.0/test.sh b/python/compatibility_tests/v2.5.0/test.sh
index fb3e545..f983ea2 100755
--- a/python/compatibility_tests/v2.5.0/test.sh
+++ b/python/compatibility_tests/v2.5.0/test.sh
@@ -12,7 +12,7 @@
 # The old version of protobuf that we are testing compatibility against. This
 # is usually the same as TEST_VERSION (i.e., we use the tests extracted from
 # that version to test compatibility of the newest runtime against it), but it
-# is also possible to use this same test set to test the compatibiilty of the
+# is also possible to use this same test set to test the compatibility of the
 # latest version against other versions.
 OLD_VERSION=$1
 OLD_VERSION_PROTOC=http://repo1.maven.org/maven2/com/google/protobuf/protoc/$OLD_VERSION/protoc-$OLD_VERSION-linux-x86_64.exe
diff --git a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/generator_test.py b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/generator_test.py
index 8343aba..feb7752 100755
--- a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/generator_test.py
+++ b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/generator_test.py
@@ -148,7 +148,7 @@
     proto = unittest_custom_options_pb2.TestMessageWithCustomOptions()
     enum_options = proto.DESCRIPTOR.enum_types_by_name['AnEnum'].GetOptions()
     self.assertTrue(enum_options is not None)
-    # TODO(gps): We really should test for the presense of the enum_opt1
+    # TODO(gps): We really should test for the presence of the enum_opt1
     # extension and for its value to be set to -789.
 
   def testNestedTypes(self):
diff --git a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/service_reflection_test.py b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/service_reflection_test.py
index 2f0708d..9b7356f 100755
--- a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/service_reflection_test.py
+++ b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/service_reflection_test.py
@@ -118,7 +118,7 @@
     rpc_controller = 'controller'
     request = 'request'
 
-    # GetDescriptor now static, still works as instance method for compatability
+    # GetDescriptor now static, still works as instance method for compatibility
     self.assertEqual(unittest_pb2.TestService_Stub.GetDescriptor(),
                      stub.GetDescriptor())
 
diff --git a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/text_format_test.py b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/text_format_test.py
index 1e6f063..0bee668 100755
--- a/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/text_format_test.py
+++ b/python/compatibility_tests/v2.5.0/tests/google/protobuf/internal/text_format_test.py
@@ -247,7 +247,7 @@
     text = text.replace('e+0','e+').replace('e+0','e+') \
                .replace('e-0','e-').replace('e-0','e-')
     # Floating point fields are printed with .0 suffix even if they are
-    # actualy integer numbers.
+    # actually integer numbers.
     text = re.compile(r'\.0$', re.MULTILINE).sub('', text)
     return text
 
diff --git a/python/google/protobuf/descriptor.py b/python/google/protobuf/descriptor.py
index 78d889a..a001409 100755
--- a/python/google/protobuf/descriptor.py
+++ b/python/google/protobuf/descriptor.py
@@ -186,7 +186,7 @@
         file.serialized_pb that describes this descriptor.
       serialized_end: The end index (exclusive) in block in the
         file.serialized_pb that describes this descriptor.
-      serialized_options: Protocol message serilized options or None.
+      serialized_options: Protocol message serialized options or None.
     """
     super(_NestedDescriptorBase, self).__init__(
         options, serialized_options, options_class_name)
@@ -753,7 +753,7 @@
     name: (str) Name of the service.
     full_name: (str) Full name of the service, including package name.
     index: (int) 0-indexed index giving the order that this services
-      definition appears withing the .proto file.
+      definition appears within the .proto file.
     methods: (list of MethodDescriptor) List of methods provided by this
       service.
     methods_by_name: (dict str -> MethodDescriptor) Same MethodDescriptor
diff --git a/python/google/protobuf/descriptor_pool.py b/python/google/protobuf/descriptor_pool.py
index d99d3f8..9a4f1cc 100644
--- a/python/google/protobuf/descriptor_pool.py
+++ b/python/google/protobuf/descriptor_pool.py
@@ -639,7 +639,7 @@
     return list(self._extensions_by_number[message_descriptor].values())
 
   def _TryLoadExtensionFromDB(self, message_descriptor, number):
-    """Try to Load extensions from decriptor db.
+    """Try to Load extensions from descriptor db.
 
     Args:
       message_descriptor: descriptor of the extended message.
@@ -1034,7 +1034,7 @@
 
     Args:
       field_proto: Data about the field in proto format.
-      field_desc: The descriptor to modiy.
+      field_desc: The descriptor to modify.
       package: The package the field's container is in.
       scope: Enclosing scope of available types.
     """
diff --git a/python/google/protobuf/internal/extension_dict.py b/python/google/protobuf/internal/extension_dict.py
index a44bf9d..d08df4a 100644
--- a/python/google/protobuf/internal/extension_dict.py
+++ b/python/google/protobuf/internal/extension_dict.py
@@ -139,7 +139,7 @@
 
   # Note that this is only meaningful for non-repeated, scalar extension
   # fields.  Note also that we may have to call _Modified() when we do
-  # successfully set a field this way, to set any necssary "has" bits in the
+  # successfully set a field this way, to set any necessary "has" bits in the
   # ancestors of the extended message.
   def __setitem__(self, extension_handle, value):
     """If extension_handle specifies a non-repeated, scalar extension
diff --git a/python/google/protobuf/internal/text_format_test.py b/python/google/protobuf/internal/text_format_test.py
index aa6f97b..8952088 100755
--- a/python/google/protobuf/internal/text_format_test.py
+++ b/python/google/protobuf/internal/text_format_test.py
@@ -97,7 +97,7 @@
     text = text.replace('e+0','e+').replace('e+0','e+') \
                .replace('e-0','e-').replace('e-0','e-')
     # Floating point fields are printed with .0 suffix even if they are
-    # actualy integer numbers.
+    # actually integer numbers.
     text = re.compile(r'\.0$', re.MULTILINE).sub('', text)
     return text
 
diff --git a/python/google/protobuf/internal/type_checkers.py b/python/google/protobuf/internal/type_checkers.py
index ac1fbbf..8deba47 100755
--- a/python/google/protobuf/internal/type_checkers.py
+++ b/python/google/protobuf/internal/type_checkers.py
@@ -38,7 +38,7 @@
 TYPE_TO_SERIALIZE_METHOD: A dictionary with field types and serialization
   function.
 FIELD_TYPE_TO_WIRE_TYPE: A dictionary with field typed and their
-  coresponding wire types.
+  corresponding wire types.
 TYPE_TO_DESERIALIZE_METHOD: A dictionary with field types and deserialization
   function.
 """
diff --git a/python/google/protobuf/json_format.py b/python/google/protobuf/json_format.py
index a11874d..5c8ef9e 100644
--- a/python/google/protobuf/json_format.py
+++ b/python/google/protobuf/json_format.py
@@ -265,7 +265,7 @@
           else:
             name = field.json_name
           if name in js:
-            # Skip the field which has been serailized already.
+            # Skip the field which has been serialized already.
             continue
           if _IsMapEntry(field):
             js[name] = {}
diff --git a/python/google/protobuf/pyext/descriptor.cc b/python/google/protobuf/pyext/descriptor.cc
index 6b1f427..24b2b46 100644
--- a/python/google/protobuf/pyext/descriptor.cc
+++ b/python/google/protobuf/pyext/descriptor.cc
@@ -481,7 +481,7 @@
 }
 
 static PyObject* GetConcreteClass(PyBaseDescriptor* self, void *closure) {
-  // Retuns the canonical class for the given descriptor.
+  // Returns the canonical class for the given descriptor.
   // This is the class that was registered with the primary descriptor pool
   // which contains this descriptor.
   // This might not be the one you expect! For example the returned object does
diff --git a/python/google/protobuf/pyext/unknown_fields.cc b/python/google/protobuf/pyext/unknown_fields.cc
index c3679c0..8509213 100755
--- a/python/google/protobuf/pyext/unknown_fields.cc
+++ b/python/google/protobuf/pyext/unknown_fields.cc
@@ -246,7 +246,7 @@
     return NULL;
   }
 
-  // Assign a default value to suppress may-unintialized warnings (errors
+  // Assign a default value to suppress may-uninitialized warnings (errors
   // when built in some places).
   WireFormatLite::WireType wire_type = WireFormatLite::WIRETYPE_VARINT;
   switch (unknown_field->type()) {
diff --git a/python/mox.py b/python/mox.py
index 43db021..9dd8ac7 100755
--- a/python/mox.py
+++ b/python/mox.py
@@ -705,7 +705,7 @@
     """Move this method into group of calls which may be called multiple times.
 
     A group of repeating calls must be defined together, and must be executed in
-    full before the next expected mehtod can be called.
+    full before the next expected method can be called.
 
     Args:
       group_name: the name of the unordered group.