diff --git a/.travis.yml b/.travis.yml
index 8471d0d3c61..c2e753a867e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,6 +21,7 @@ cache:
   directories:
     - $HOME/bazel/install
     - $HOME/bazel/outbase
+    - $HOME/clang
 
 before_install:
   - mkdir -p ${HOME}/bazel/install
@@ -34,6 +35,7 @@ before_install:
   - cat .bazelrc.travis .bazelrc.orig > .bazelrc
 
 script:
+  - script/check-style
   - bazel --output_base=${HOME}/bazel/outbase test //...
 
 notifications:
diff --git a/contrib/endpoints/src/api_manager/config.cc b/contrib/endpoints/src/api_manager/config.cc
index dcd3d15dcc5..b0a1b85d119 100644
--- a/contrib/endpoints/src/api_manager/config.cc
+++ b/contrib/endpoints/src/api_manager/config.cc
@@ -258,7 +258,7 @@ bool Config::LoadRpcMethods(ApiManagerEnvInterface *env,
 bool Config::LoadAuthentication(ApiManagerEnvInterface *env) {
   // Parsing auth config.
   const ::google::api::Authentication &auth = service_.authentication();
-  map<string, const ::google::api::AuthProvider*> provider_id_provider_map;
+  map<string, const ::google::api::AuthProvider *> provider_id_provider_map;
   for (const auto &provider : auth.providers()) {
     if (provider.id().empty()) {
       env->LogError("Missing id field in AuthProvider.");
@@ -296,15 +296,15 @@ bool Config::LoadAuthentication(ApiManagerEnvInterface *env) {
         env->LogError(error.c_str());
         continue;
       }
-      auto provider = utils::FindPtrOrNull(provider_id_provider_map,
-                                           provider_id);
+      auto provider =
+          utils::FindPtrOrNull(provider_id_provider_map, provider_id);
       if (provider == nullptr) {
         std::string error = "Undefined provider_id: " + provider_id;
         env->LogError(error.c_str());
       } else {
         const std::string &audiences = provider->audiences().empty()
-                              ? requirement.audiences()
-                              : provider->audiences();
+                                           ? requirement.audiences()
+                                           : provider->audiences();
         (*method)->addAudiencesForIssuer(provider->issuer(), audiences);
       }
     }
diff --git a/script/check-style b/script/check-style
new file mode 100755
index 00000000000..443fabd087f
--- /dev/null
+++ b/script/check-style
@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Copyright 2016 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+#
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+# Install required clang version to a folder and cache it.
+CLANG_VERSION_REQUIRED="3.8.0"
+CLANG_DIRECTORY="${HOME}/clang"
+CLANG_FORMAT="${CLANG_DIRECTORY}/bin/clang-format"
+
+CLANG_VERSION="$(${CLANG_FORMAT} -version | cut -d ' ' -f 3)"
+if [[ "${CLANG_VERSION}" != "${CLANG_VERSION_REQUIRED}" ]]; then
+  echo "Installing required clang-format ${CLANG_VERSION_REQUIRED} to ${CLANG_DIRECTORY}"
+  mkdir -p ${CLANG_DIRECTORY}
+  curl --silent --show-error --retry 10 \
+    "http://releases.llvm.org/${CLANG_VERSION_REQUIRED}/clang+llvm-${CLANG_VERSION_REQUIRED}-x86_64-linux-gnu-ubuntu-14.04.tar.xz" \
+    | tar Jx -C "${CLANG_DIRECTORY}" --strip=1 \
+  || { echo "Could not install required clang-format. Skip formating." ; exit 0 ; }
+fi
+
+echo "Checking file format ..."
+
+pushd ${ROOT} > /dev/null
+
+SOURCE_FILES=($(git ls-tree -r HEAD --name-only | grep -E '\.(h|c|cc|proto)$'))
+"${CLANG_FORMAT}" -style=Google -i "${SOURCE_FILES[@]}" \
+  || { echo "Could not run clang-format." ; exit 1 ; }
+
+CHANGED_FILES=($(git diff HEAD --name-only | grep -E '\.(h|c|cc|proto)$'))
+
+if [[ "${#CHANGED_FILES}" -ne 0 ]]; then
+  echo "Files not formatted: ${CHANGED_FILES[@]}"
+  exit 1
+fi
+echo "All files are properly formatted."
+
+popd
diff --git a/src/envoy/prototype/api_manager_env.cc b/src/envoy/prototype/api_manager_env.cc
index d694fab49a2..0ef8cb004d5 100644
--- a/src/envoy/prototype/api_manager_env.cc
+++ b/src/envoy/prototype/api_manager_env.cc
@@ -24,7 +24,6 @@ void Http::ApiManager::Env::Log(LogLevel level, const char *message) {
   }
 }
 
-
 class PeriodicTimer : public google::api_manager::PeriodicTimer,
                       public Logger::Loggable<Logger::Id::http> {
  private:
@@ -73,9 +72,8 @@ class HTTPRequest : public Http::Message {
     header_map_.addStatic(Headers::get().Scheme, "http");
     header_map_.addStatic(Headers::get().Host, "localhost");
     header_map_.addStatic(Headers::get().ContentLength,
-                           std::to_string(body_.length()));
-    header_map_.addStatic(LowerCaseString("x-api-manager-url"),
-                           request->url());
+                          std::to_string(body_.length()));
+    header_map_.addStatic(LowerCaseString("x-api-manager-url"), request->url());
     for (auto header : request->request_headers()) {
       LowerCaseString key(header.first);
       header_map_.addStatic(key, header.second);
@@ -102,10 +100,11 @@ class RequestCallbacks : public AsyncClient::Callbacks {
         std::stoi(response->headers().Status()->value().c_str()), "");
     std::map<std::string, std::string> headers;
     response->headers().iterate(
-        [&](const HeaderEntry& header, void*) -> void {
+        [&](const HeaderEntry &header, void *) -> void {
           // TODO: fix it
           // headers.emplace(header.key().c_str(), header.value().c_str());
-        }, nullptr);
+        },
+        nullptr);
     request_->OnComplete(status, std::move(headers), response->bodyAsString());
     delete this;
   }
diff --git a/src/envoy/prototype/api_manager_env.h b/src/envoy/prototype/api_manager_env.h
index ea045532ae2..6e5e63676aa 100644
--- a/src/envoy/prototype/api_manager_env.h
+++ b/src/envoy/prototype/api_manager_env.h
@@ -3,8 +3,8 @@
 #include "precompiled/precompiled.h"
 
 #include "common/common/logger.h"
-#include "envoy/upstream/cluster_manager.h"
 #include "contrib/endpoints/include/api_manager/env_interface.h"
+#include "envoy/upstream/cluster_manager.h"
 #include "server/server.h"
 
 namespace Http {
diff --git a/src/envoy/prototype/api_manager_filter.cc b/src/envoy/prototype/api_manager_filter.cc
index d54258e30c4..d310508a592 100644
--- a/src/envoy/prototype/api_manager_filter.cc
+++ b/src/envoy/prototype/api_manager_filter.cc
@@ -1,15 +1,15 @@
 #include "precompiled/precompiled.h"
 
 #include "api_manager_env.h"
-#include "common/grpc/common.h"
 #include "common/common/logger.h"
+#include "common/grpc/common.h"
 #include "common/http/filter/ratelimit.h"
 #include "common/http/headers.h"
 #include "common/http/utility.h"
-#include "envoy/server/instance.h"
 #include "contrib/endpoints/include/api_manager/api_manager.h"
-#include "server/config/network/http_connection_manager.h"
 #include "contrib/endpoints/src/grpc/transcoding/transcoder.h"
+#include "envoy/server/instance.h"
+#include "server/config/network/http_connection_manager.h"
 
 namespace Http {
 namespace ApiManager {
@@ -157,7 +157,7 @@ class Instance : public Http::StreamFilter,
   FilterDataStatus decodeData(Buffer::Instance& data,
                               bool end_stream) override {
     log().debug("Called ApiManager::Instance : {} ({}, {})", __func__,
-                 data.length(), end_stream);
+                data.length(), end_stream);
     if (state_ == Calling) {
       return FilterDataStatus::StopIterationAndBuffer;
     }
@@ -180,7 +180,7 @@ class Instance : public Http::StreamFilter,
   }
   void completeCheck(const google::api_manager::utils::Status& status) {
     log().debug("Called ApiManager::Instance : check complete {}",
-                 status.ToJson());
+                status.ToJson());
     if (!status.ok() && state_ != Responded) {
       state_ = Responded;
       Utility::sendLocalReply(*decoder_callbacks_, Code(status.HttpCode()),