diff --git a/lib/serve/application.rb b/lib/serve/application.rb
index ad4c1f4..6d588eb 100644
--- a/lib/serve/application.rb
+++ b/lib/serve/application.rb
@@ -160,7 +160,8 @@ def extract_environment(args)
       end
       
       def extract_port(args)
-        (args.delete(args.find {|a| /^\d\d\d*$/.match(a) }) || ((rails_app? or rack_app?) ? 3000 : 4000)).to_i
+        default_port = rails_app? ? 3000 : 4000
+        (args.delete(args.find {|a| /^\d\d\d*$/.match(a) }) || ENV['PORT'] || default_port).to_i
       end
       
       def extract_address(args)
diff --git a/lib/serve/bootstrap/config.ru b/lib/serve/bootstrap/config.ru
index 82dd519..0310065 100644
--- a/lib/serve/bootstrap/config.ru
+++ b/lib/serve/bootstrap/config.ru
@@ -1,5 +1,3 @@
-#\ -p 4000
-
 require 'rubygems'
 require 'bundler'
 begin
@@ -44,4 +42,4 @@ else
     Serve::RackAdapter.new(root + '/views'),
     Rack::Directory.new(root + '/public')
   ])
-end
\ No newline at end of file
+end
diff --git a/spec/application_spec.rb b/spec/application_spec.rb
index b176da1..88f1dc7 100644
--- a/spec/application_spec.rb
+++ b/spec/application_spec.rb
@@ -38,6 +38,11 @@
     it "with the port, address, and protocol" do
       parse('http://1.1.1.1:2000').should == @options.update(:address => "1.1.1.1", :port=>2000)
     end
+
+    it "with port set in ENV" do
+      ENV["PORT"] = "4321"
+      parse[:port].should == 4321
+    end
     
     it "help" do
       parse('')[:help].should be_false
@@ -150,4 +155,4 @@ def parse(*args)
     
   end
   
-end
\ No newline at end of file
+end
diff --git a/website/config.ru b/website/config.ru
index 7f8dfad..ce48a2a 100644
--- a/website/config.ru
+++ b/website/config.ru
@@ -1,5 +1,3 @@
-#\ -p 4000
-
 require 'rubygems'
 require 'bundler'
 begin