diff --git a/gunicorn/arbiter.py b/gunicorn/arbiter.py
index e23f1bde..19f9fa74 100644
--- a/gunicorn/arbiter.py
+++ b/gunicorn/arbiter.py
@@ -32,13 +32,14 @@ class Arbiter(object):
         if name[:3] == "SIG" and name[3] != "_"
     )
     
-    def __init__(self, address, num_workers, modname):
+    def __init__(self, address, num_workers, modname, debug=False):
         self.address = address
         self.num_workers = num_workers
         self.modname = modname
         self.timeout = 30
         self.reexec_pid = 0
         self.pid = os.getpid()
+        self.debug = debug
         self.log = logging.getLogger(__name__)
         self.init_signals()
         self.listen(self.address)
@@ -270,7 +271,7 @@ class Arbiter(object):
                 continue
 
             worker = Worker(i, self.pid, self.LISTENER, self.modname,
-                        self.timeout)
+                        self.timeout, self.debug)
             pid = os.fork()
             if pid != 0:
                 self.WORKERS[pid] = worker
diff --git a/gunicorn/http/request.py b/gunicorn/http/request.py
index d6ff7b84..9721a5b1 100644
--- a/gunicorn/http/request.py
+++ b/gunicorn/http/request.py
@@ -43,7 +43,9 @@ class HttpRequest(object):
     }
 
 
-    def __init__(self, socket, client_address, server_address):
+    def __init__(self, socket, client_address, server_address, 
+            debug=False):
+        self.debug = debug
         self.socket = socket
         self.client_address = client_address
         self.server_address = server_address
@@ -82,13 +84,24 @@ class HttpRequest(object):
         else:
             wsgi_input = TeeInput(self.socket, self.parser, buf[i:])
                 
+                
+        if self.debug:
+            # according to the doc 
+            # This value should evaluate true if an equivalent application object
+            # may be simultaneously invoked by another process, and should evaluate
+            # false otherwise. In debug mode we fall to one worker
+            # so we comply to pylons and other paster app.
+            wsgi_multiprocess = False
+        else:
+            wsgi_multiprocess = True
+            
         environ = {
             "wsgi.url_scheme": 'http',
             "wsgi.input": wsgi_input,
             "wsgi.errors": sys.stderr,
             "wsgi.version": (1, 0),
             "wsgi.multithread": False,
-            "wsgi.multiprocess": True,
+            "wsgi.multiprocess": wsgi_multiprocess,
             "wsgi.run_once": False,
             "SCRIPT_NAME": "",
             "SERVER_SOFTWARE": self.SERVER_VERSION,
diff --git a/gunicorn/main.py b/gunicorn/main.py
index 919bb177..5e89147d 100644
--- a/gunicorn/main.py
+++ b/gunicorn/main.py
@@ -28,7 +28,9 @@ def options():
         op.make_option('--log-level', dest='loglevel', default='info',
             help='Log level below which to silence messages. [%default]'),
         op.make_option('--log-file', dest='logfile', default='-',
-            help='Log to a file. - is stdout. [%default]')
+            help='Log to a file. - is stdout. [%default]'),
+        op.make_option('-d', '--debug', dest='debug', action="store_true",
+            default=False, help='Debug mode. only 1 worker.')
     ]
 
 def configure_logging(opts):
@@ -52,7 +54,12 @@ def main(usage, get_app):
     configure_logging(opts)
 
     app = get_app(parser, opts, args)
-    arbiter = Arbiter((opts.host, opts.port), opts.workers, app)
+    workers = opts.workers
+    if opts.debug:
+        workers = 1
+    
+    arbiter = Arbiter((opts.host, opts.port), workers, app, 
+                    opts.debug)
     arbiter.run()
     
 def paste_server(app, global_conf=None, host="127.0.0.1", port=None, 
@@ -69,5 +76,11 @@ def paste_server(app, global_conf=None, host="127.0.0.1", port=None,
     else:
         workers = int(global_conf.get('workers', 1))
     
-    arbiter = Arbiter(bind_addr, workers, app)
+    debug = global_conf.get('debug') == "true"
+    if debug:
+        # we force to one worker in debug mode.
+        workers = 1
+    
+    arbiter = Arbiter(bind_addr, workers, app, 
+                    debug)
     arbiter.run()
\ No newline at end of file
diff --git a/gunicorn/worker.py b/gunicorn/worker.py
index e6d9874a..9ac365aa 100644
--- a/gunicorn/worker.py
+++ b/gunicorn/worker.py
@@ -25,9 +25,11 @@ class Worker(object):
         "HUP QUIT INT TERM TTIN TTOU USR1".split()
     )
 
-    def __init__(self, workerid, ppid, socket, app, timeout):
+    def __init__(self, workerid, ppid, socket, app, timeout,
+            debug=False):
         self.id = workerid
         self.ppid = ppid
+        self.debug = debug
         self.timeout = timeout / 2.0
         fd, tmpname = tempfile.mkstemp()
         self.tmp = os.fdopen(fd, "r+b")
@@ -115,7 +117,7 @@ class Worker(object):
     def handle(self, client, addr):
         util.close_on_exec(client)
         try:
-            req = http.HttpRequest(client, addr, self.address)
+            req = http.HttpRequest(client, addr, self.address, self.debug)
             try:
                 response = self.app(req.read(), req.start_response)
             except Exception, e:
diff --git a/setup.py b/setup.py
index abd42136..695a8120 100644
--- a/setup.py
+++ b/setup.py
@@ -45,5 +45,4 @@ setup(
     main=gunicorn.main:paste_server
     """,
     test_suite = 'nose.collector',
-)
-
+)
\ No newline at end of file