Index: lib/net/http.rb
===================================================================
--- lib/net/http.rb	(revision 29217)
+++ lib/net/http.rb	(working copy)
@@ -517,6 +517,7 @@
       @started = false
       @open_timeout = nil
       @read_timeout = 60
+      @continue_timeout = nil
       @debug_output = nil
       @use_ssl = false
       @ssl_context = nil
@@ -570,6 +571,16 @@
       @read_timeout = sec
     end
 
+    # Seconds to wait for 100 Continue response.  If the HTTP object does not
+    # receive a response in this many seconds it sends the request body.
+    attr_reader :continue_timeout
+
+    # Setter for the continue_timeout attribute.
+    def continue_timeout=(sec)
+      @socket.continue_timeout = sec if @socket
+      @continue_timeout = sec
+    end
+
     # returns true if the HTTP session is started.
     def started?
       @started
@@ -1190,12 +1201,15 @@
 
     def transport_request(req)
       begin_transport req
-      req.exec @socket, @curr_http_version, edit_path(req.path)
-      begin
-        res = HTTPResponse.read_new(@socket)
-      end while res.kind_of?(HTTPContinue)
-      res.reading_body(@socket, req.response_body_permitted?) {
-        yield res if block_given?
+      res = catch(:response) {
+        req.exec @socket, @curr_http_version, edit_path(req.path)
+        begin
+          res = HTTPResponse.read_new(@socket)
+        end while res.kind_of?(HTTPContinue)
+        res.reading_body(@socket, req.response_body_permitted?) {
+          yield res if block_given?
+        }
+        res
       }
       end_transport req, res
       res
@@ -1739,6 +1753,7 @@
       self.content_length = body.bytesize
       delete 'Transfer-Encoding'
       supply_default_content_type
+      wait_for_continue sock, ver if sock.continue_timeout
       write_header sock, ver, path
       sock.write body
     end
@@ -1749,6 +1764,7 @@
             "Content-Length not given and Transfer-Encoding is not `chunked'"
       end
       supply_default_content_type
+      wait_for_continue sock, ver if sock.continue_timeout
       write_header sock, ver, path
       if chunked?
         while s = f.read(1024)
@@ -1768,6 +1784,22 @@
       set_content_type 'application/x-www-form-urlencoded'
     end
 
+    ##
+    # Waits up to the continue timeout for a response from the server provided
+    # we're speaking HTTP 1.1 and are expecting a 100-continue response.
+
+    def wait_for_continue(sock, ver)
+      if ver >= '1.1' and @header['expect'] and
+          @header['expect'].include?('100-continue') then
+        if IO.select [sock.io], nil, nil, sock.continue_timeout then
+          res = HTTPResponse.read_new sock
+          unless res.kind_of?(Net::HTTPContinue)
+            throw :response, res
+          end
+        end
+      end
+    end
+
     def write_header(sock, ver, path)
       buf = "#{@method} #{path} HTTP/#{ver}\r\n"
       each_capitalized do |k,v|
Index: lib/net/protocol.rb
===================================================================
--- lib/net/protocol.rb	(revision 29217)
+++ lib/net/protocol.rb	(working copy)
@@ -50,12 +50,14 @@
     def initialize(io)
       @io = io
       @read_timeout = 60
+      @continue_timeout = nil
       @debug_output = nil
       @rbuf = ''
     end
 
     attr_reader :io
     attr_accessor :read_timeout
+    attr_accessor :continue_timeout
     attr_accessor :debug_output
 
     def inspect
Index: test/net/http/test_http.rb
===================================================================
--- test/net/http/test_http.rb	(revision 29217)
+++ test/net/http/test_http.rb	(working copy)
@@ -372,6 +372,87 @@
   end
 end
 
+class TestNetHTTPContinue < Test::Unit::TestCase
+  CONFIG = {
+    'host' => '127.0.0.1',
+    'port' => 10081,
+    'proxy_host' => nil,
+    'proxy_port' => nil,
+    'chunked' => true,
+  }
+
+  include TestNetHTTPUtils
+
+  def logfile
+    @debug = StringIO.new('')
+  end
+
+  def mount_proc(&block)
+    @server.mount('/continue', WEBrick::HTTPServlet::ProcHandler.new(block.to_proc))
+  end
+
+  def test_expect_continue
+    mount_proc {|req, res|
+      req.continue
+      res.body = req.query['body']
+    }
+    start {|http|
+      http.continue_timeout = 0.2
+      http.request_post('/continue', 'body=BODY', 'expect' => '100-continue') {|res|
+        assert_equal('BODY', res.read_body)
+      }
+    }
+    assert_match(/Expect: 100-continue/, @debug.string)
+    assert_match(/HTTP\/1.1 100 continue/, @debug.string)
+  end
+
+  def test_expect_continue_timeout
+    mount_proc {|req, res|
+      sleep 0.2
+      req.continue # just ignored because it's '100'
+      res.body = req.query['body']
+    }
+    start {|http|
+      http.continue_timeout = 0
+      http.request_post('/continue', 'body=BODY', 'expect' => '100-continue') {|res|
+        assert_equal('BODY', res.read_body)
+      }
+    }
+    assert_match(/Expect: 100-continue/, @debug.string)
+    assert_match(/HTTP\/1.1 100 continue/, @debug.string)
+  end
+
+  def test_expect_continue_error
+    mount_proc {|req, res|
+      res.status = 501
+      res.body = req.query['body']
+    }
+    start {|http|
+      http.continue_timeout = 0
+      http.request_post('/continue', 'body=ERROR', 'expect' => '100-continue') {|res|
+        assert_equal('ERROR', res.read_body)
+      }
+    }
+    assert_match(/Expect: 100-continue/, @debug.string)
+    assert_not_match(/HTTP\/1.1 100 continue/, @debug.string)
+  end
+
+  def test_expect_continue_error_while_waiting
+    mount_proc {|req, res|
+      res.status = 501
+      res.body = req.query['body']
+    }
+    start {|http|
+      http.continue_timeout = 0.5
+      http.request_post('/continue', 'body=ERROR', 'expect' => '100-continue') {|res|
+        assert_equal('ERROR', res.read_body)
+      }
+    }
+    assert_match(/Expect: 100-continue/, @debug.string)
+    assert_not_match(/HTTP\/1.1 100 continue/, @debug.string)
+  end
+end
+
 =begin
 class TestNetHTTP_proxy < Test::Unit::TestCase
   CONFIG = {