diff --git a/src/nghttp.cc b/src/nghttp.cc
index dad9652f..c9f219ac 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -113,7 +113,8 @@ Config::Config()
       no_content_length(false),
       no_dep(false),
       hexdump(false),
-      no_push(false) {
+      no_push(false),
+      expect_continue(false) {
   nghttp2_option_new(&http2_option);
   nghttp2_option_set_peer_max_concurrent_streams(http2_option,
                                                  peer_max_concurrent_streams);
@@ -303,6 +304,51 @@ void Request::record_response_end_time() {
   timing.response_end_time = get_time();
 }
 
+namespace {
+void continue_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
+  auto client = static_cast<HttpClient *>(ev_userdata(loop));
+  auto req = static_cast<Request *>(w->data);
+  int error;
+
+  error = nghttp2_submit_data(client->session, NGHTTP2_FLAG_END_STREAM,
+                              req->stream_id, req->data_prd);
+
+  if (error) {
+    std::cerr << "[ERROR] nghttp2_submit_data() returned error: "
+              << nghttp2_strerror(error) << std::endl;
+    nghttp2_submit_rst_stream(client->session, NGHTTP2_FLAG_NONE,
+                              req->stream_id, NGHTTP2_INTERNAL_ERROR);
+  }
+
+  client->signal_write();
+}
+} // namespace
+
+ContinueTimer::ContinueTimer(struct ev_loop *loop, Request *req)
+    : loop(loop) {
+  ev_timer_init(&timer, continue_timeout_cb, 1., 0.);
+  timer.data = req;
+}
+
+ContinueTimer::~ContinueTimer() {
+  stop();
+}
+
+void ContinueTimer::start() {
+  ev_timer_start(loop, &timer);
+}
+
+void ContinueTimer::stop() {
+  ev_timer_stop(loop, &timer);
+}
+
+void ContinueTimer::dispatch_continue() {
+  // Only dispatch the timeout callback if it hasn't already been called.
+  if (ev_is_active(&timer)) {
+    ev_feed_event(loop, &timer, 0);
+  }
+}
+
 namespace {
 int htp_msg_begincb(http_parser *htp) {
   if (config.verbose) {
@@ -353,16 +399,27 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
                                {"accept", "*/*"},
                                {"accept-encoding", "gzip, deflate"},
                                {"user-agent", "nghttp2/" NGHTTP2_VERSION}};
+  bool expect_continue = false;
+
   if (config.continuation) {
     for (size_t i = 0; i < 6; ++i) {
       build_headers.emplace_back("continuation-test-" + util::utos(i + 1),
                                  std::string(4_k, '-'));
     }
   }
+
   auto num_initial_headers = build_headers.size();
-  if (!config.no_content_length && req->data_prd) {
-    build_headers.emplace_back("content-length", util::utos(req->data_length));
+
+  if (req->data_prd) {
+    if (!config.no_content_length) {
+      build_headers.emplace_back("content-length", util::utos(req->data_length));
+    }
+    if (config.expect_continue) {
+      expect_continue = true;
+      build_headers.emplace_back("expect", "100-continue");
+    }
   }
+
   for (auto &kv : headers) {
     size_t i;
     for (i = 0; i < num_initial_headers; ++i) {
@@ -400,11 +457,21 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
     nva.push_back(http2::make_nv_ls("trailer", trailer_names));
   }
 
-  auto stream_id =
-      nghttp2_submit_request(client->session, &req->pri_spec, nva.data(),
-                             nva.size(), req->data_prd, req);
+  int32_t stream_id;
+
+  if (expect_continue) {
+    stream_id = nghttp2_submit_headers(client->session, 0, -1, &req->pri_spec,
+                               nva.data(), nva.size(), req);
+  } else {
+    stream_id =
+        nghttp2_submit_request(client->session, &req->pri_spec, nva.data(),
+                               nva.size(), req->data_prd, req);
+  }
+
   if (stream_id < 0) {
-    std::cerr << "[ERROR] nghttp2_submit_request() returned error: "
+    std::cerr << "[ERROR] nghttp2_submit_"
+              << (expect_continue ? "headers" : "request")
+              << "() returned error: "
               << nghttp2_strerror(stream_id) << std::endl;
     return -1;
   }
@@ -414,6 +481,11 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
 
   req->req_nva = std::move(build_headers);
 
+  if (expect_continue) {
+    auto timer = make_unique<ContinueTimer>(client->loop, req);
+    req->continue_timer = std::move(timer);
+  }
+
   return 0;
 }
 } // namespace
@@ -614,6 +686,12 @@ int HttpClient::initiate_connection() {
 void HttpClient::disconnect() {
   state = ClientState::IDLE;
 
+  for (auto req = std::begin(reqvec); req != std::end(reqvec); ++req) {
+    if ((*req)->continue_timer) {
+      (*req)->continue_timer->stop();
+    }
+  }
+
   ev_timer_stop(loop, &settings_timer);
 
   ev_timer_stop(loop, &rt);
@@ -1616,11 +1694,19 @@ void check_response_header(nghttp2_session *session, Request *req) {
   }
 
   if (req->status / 100 == 1) {
+    if (req->continue_timer && (req->status == 100)) {
+      // If the request is waiting for a 100 Continue, complete the handshake.
+      req->continue_timer->dispatch_continue();
+    }
+
     req->expect_final_response = true;
     req->status = 0;
     req->res_nva.clear();
     http2::init_hdidx(req->res_hdidx);
     return;
+  } else if (req->continue_timer) {
+    // A final response stops any pending Expect/Continue handshake.
+    req->continue_timer->stop();
   }
 
   if (gzip) {
@@ -1895,6 +1981,34 @@ int before_frame_send_callback(nghttp2_session *session,
 
 } // namespace
 
+namespace {
+int on_frame_send_callback(nghttp2_session *session,
+                           const nghttp2_frame *frame,
+                           void *user_data) {
+  if (config.verbose) {
+    verbose_on_frame_send_callback(session, frame, user_data);
+  }
+
+  if (frame->hd.type != NGHTTP2_HEADERS ||
+      frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
+    return 0;
+  }
+
+  auto req = static_cast<Request *>(
+      nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+  if (!req) {
+    return 0;
+  }
+
+  // If this request is using Expect/Continue, start its ContinueTimer.
+  if (req->continue_timer) {
+    req->continue_timer->start();
+  }
+
+  return 0;
+}
+} // namespace
+
 namespace {
 int on_frame_not_send_callback(nghttp2_session *session,
                                const nghttp2_frame *frame, int lib_error_code,
@@ -1928,6 +2042,11 @@ int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
     return 0;
   }
 
+  // If this request is using Expect/Continue, stop its ContinueTimer.
+  if (req->continue_timer) {
+    req->continue_timer->stop();
+  }
+
   update_html_parser(client, req, nullptr, 0, 1);
   ++client->complete;
 
@@ -2138,7 +2257,10 @@ int communicate(
                 << std::endl;
       goto fin;
     }
+
+    ev_set_userdata(loop, &client);
     ev_run(loop, 0);
+    ev_set_userdata(loop, nullptr);
 
 #ifdef HAVE_JANSSON
     if (!config.harfile.empty()) {
@@ -2251,9 +2373,6 @@ int run(char **uris, int n) {
                                                        on_frame_recv_callback2);
 
   if (config.verbose) {
-    nghttp2_session_callbacks_set_on_frame_send_callback(
-        callbacks, verbose_on_frame_send_callback);
-
     nghttp2_session_callbacks_set_on_invalid_frame_recv_callback(
         callbacks, verbose_on_invalid_frame_recv_callback);
 
@@ -2273,6 +2392,9 @@ int run(char **uris, int n) {
   nghttp2_session_callbacks_set_before_frame_send_callback(
       callbacks, before_frame_send_callback);
 
+  nghttp2_session_callbacks_set_on_frame_send_callback(
+      callbacks, on_frame_send_callback);
+
   nghttp2_session_callbacks_set_on_frame_not_send_callback(
       callbacks, on_frame_not_send_callback);
 
@@ -2503,6 +2625,11 @@ Options:
   --max-concurrent-streams=<N>
               The  number of  concurrent  pushed  streams this  client
               accepts.
+  --expect-continue
+              Perform an Expect/Continue handshake:  wait to send DATA
+              (up to  a short  timeout)  until the server sends  a 100
+              Continue interim response. This option is ignored unless
+              combined with the -d option.
   --version   Display version information and exit.
   -h, --help  Display this help and exit.
 
@@ -2554,6 +2681,7 @@ int main(int argc, char **argv) {
         {"hexdump", no_argument, &flag, 10},
         {"no-push", no_argument, &flag, 11},
         {"max-concurrent-streams", required_argument, &flag, 12},
+        {"expect-continue", no_argument, &flag, 13},
         {nullptr, 0, nullptr, 0}};
     int option_index = 0;
     int c = getopt_long(argc, argv, "M:Oab:c:d:gm:np:r:hH:vst:uw:W:",
@@ -2751,6 +2879,10 @@ int main(int argc, char **argv) {
         // max-concurrent-streams option
         config.max_concurrent_streams = strtoul(optarg, nullptr, 10);
         break;
+      case 13:
+        // expect-continue option
+        config.expect_continue = true;
+        break;
       }
       break;
     default:
diff --git a/src/nghttp.h b/src/nghttp.h
index df4ca685..fd433b84 100644
--- a/src/nghttp.h
+++ b/src/nghttp.h
@@ -91,6 +91,7 @@ struct Config {
   bool no_dep;
   bool hexdump;
   bool no_push;
+  bool expect_continue;
 };
 
 enum class RequestState { INITIAL, ON_REQUEST, ON_RESPONSE, ON_COMPLETE };
@@ -109,6 +110,23 @@ struct RequestTiming {
   RequestTiming() : state(RequestState::INITIAL) {}
 };
 
+struct Request; // forward declaration for ContinueTimer
+
+struct ContinueTimer {
+  ContinueTimer(struct ev_loop *loop, Request *req);
+  ~ContinueTimer();
+
+  void start();
+  void stop();
+
+  // Schedules an immediate run of the continue callback on the loop, if the
+  // callback has not already been run
+  void dispatch_continue();
+
+  struct ev_loop *loop;
+  ev_timer timer;
+};
+
 struct Request {
   // For pushed request, |uri| is empty and |u| is zero-cleared.
   Request(const std::string &uri, const http_parser_url &u,
@@ -156,6 +174,8 @@ struct Request {
   // used for incoming PUSH_PROMISE
   http2::HeaderIndex req_hdidx;
   bool expect_final_response;
+  // only assigned if this request is using Expect/Continue
+  std::unique_ptr<ContinueTimer> continue_timer;
 };
 
 struct SessionTiming {