diff --git a/libmproxy/flow.py b/libmproxy/flow.py
index 13b5acbcf..d174b41fa 100644
--- a/libmproxy/flow.py
+++ b/libmproxy/flow.py
@@ -323,6 +323,18 @@ class Flow:
                 self.response.ack()
             self.intercepting = False
 
+    def replace(self, pattern, repl, count=0, flags=0):
+        """
+            Replaces a regular expression pattern with repl in all parts of the
+            flow . Returns the number of replacements made. 
+        """
+        c = self.request.replace(pattern, repl, count, flags)
+        if self.response:
+            c += self.response.replace(pattern, repl, count, flags)
+        if self.error:
+            c += self.error.replace(pattern, repl, count, flags)
+        return c
+
 
 class State:
     def __init__(self):
diff --git a/libmproxy/proxy.py b/libmproxy/proxy.py
index a7cc31e86..c5e5971ac 100644
--- a/libmproxy/proxy.py
+++ b/libmproxy/proxy.py
@@ -280,6 +280,16 @@ class Request(controller.Msg):
         else:
             return self.FMT_PROXY % (self.method, self.scheme, self.host, self.port, self.path, str(headers), content)
 
+    def replace(self, pattern, repl, count=0, flags=0):
+        """
+            Replaces a regular expression pattern with repl in both the headers
+            and the body of the request. Returns the number of replacements
+            made. 
+        """
+        self.content, c = re.subn(pattern, repl, self.content, count, flags)
+        c += self.headers.replace(pattern, repl, count, flags)
+        return c
+
 
 class Response(controller.Msg):
     FMT = '%s\r\n%s\r\n%s'
@@ -406,6 +416,16 @@ class Response(controller.Msg):
         data = (proto, str(headers), content)
         return self.FMT%data
 
+    def replace(self, pattern, repl, count=0, flags=0):
+        """
+            Replaces a regular expression pattern with repl in both the headers
+            and the body of the response. Returns the number of replacements
+            made. 
+        """
+        self.content, c = re.subn(pattern, repl, self.content, count, flags)
+        c += self.headers.replace(pattern, repl, count, flags)
+        return c
+
 
 class ClientDisconnect(controller.Msg):
     def __init__(self, client_conn):
@@ -473,6 +493,15 @@ class Error(controller.Msg):
     def __eq__(self, other):
         return self.get_state() == other.get_state()
 
+    def replace(self, pattern, repl, count=0, flags=0):
+        """
+            Replaces a regular expression pattern with repl in both the headers
+            and the body of the request. Returns the number of replacements
+            made. 
+        """
+        self.msg, c = re.subn(pattern, repl, self.msg, count, flags)
+        return c
+
 
 class FileLike:
     def __init__(self, o):
diff --git a/libmproxy/utils.py b/libmproxy/utils.py
index 4d8c7c41c..9ac9c0b8f 100644
--- a/libmproxy/utils.py
+++ b/libmproxy/utils.py
@@ -279,6 +279,21 @@ class Headers:
                     ret.append([name, value])
         self.lst = ret
 
+    def replace(self, pattern, repl, count=0, flags=0):
+        """
+            Replaces a regular expression pattern with repl in both header keys
+            and values. Returns the number of replacements made. 
+        """
+        nlst, count = [], 0
+        for i in self.lst:
+            k, c = re.subn(pattern, repl, i[0], count, flags)
+            count += c
+            v, c = re.subn(pattern, repl, i[1], count, flags)
+            count += c
+            nlst.append([k, v])
+        self.lst = nlst
+        return count
+
 
 def pretty_size(size):
     suffixes = [
diff --git a/test/test_flow.py b/test/test_flow.py
index 365b6c584..ba276248f 100644
--- a/test/test_flow.py
+++ b/test/test_flow.py
@@ -219,6 +219,21 @@ class uFlow(libpry.AutoTree):
         f = flow.Flow(None)
         f.request = tutils.treq()
 
+    def test_replace(self):
+        f = tutils.tflow_full()
+        f.request.headers["foo"] = ["foo"]
+        f.request.content = "afoob"
+
+        f.response.headers["foo"] = ["foo"]
+        f.response.content = "afoob"
+
+        assert f.replace("foo", "bar") == 6
+
+        assert f.request.headers["bar"] == ["bar"]
+        assert f.request.content == "abarb"
+        assert f.response.headers["bar"] == ["bar"]
+        assert f.response.content == "abarb"
+
 
 class uState(libpry.AutoTree):
     def test_backup(self):
diff --git a/test/test_proxy.py b/test/test_proxy.py
index 46235e97d..a7627c1bc 100644
--- a/test/test_proxy.py
+++ b/test/test_proxy.py
@@ -1,4 +1,4 @@
-import cStringIO, time
+import cStringIO, time, re
 import libpry
 from libmproxy import proxy, controller, utils, dump, script
 import email.utils
@@ -128,6 +128,14 @@ class uRequest(libpry.AutoTree):
         r.load_state(r2.get_state())
         assert not r.client_conn
 
+    def test_replace(self):
+        r = tutils.treq()
+        r.headers["Foo"] = ["fOo"]
+        r.content = "afoob"
+        assert r.replace("foo", "boo", flags=re.I) == 3
+        assert not "foo" in r.content
+        assert r.headers["boo"] == ["boo"]
+
 
 class uResponse(libpry.AutoTree):
     def test_simple(self):
@@ -185,6 +193,14 @@ class uResponse(libpry.AutoTree):
         resp.load_state(resp2.get_state())
         assert resp == resp2
 
+    def test_replace(self):
+        r = tutils.tresp()
+        r.headers["Foo"] = ["fOo"]
+        r.content = "afoob"
+        assert r.replace("foo", "boo", flags=re.I) == 3
+        assert not "foo" in r.content
+        assert r.headers["boo"] == ["boo"]
+
 
 class uError(libpry.AutoTree):
     def test_getset_state(self):
@@ -203,6 +219,11 @@ class uError(libpry.AutoTree):
         e3 = e.copy()
         assert e3 == e
 
+    def test_replace(self):
+        e = proxy.Error(None, "amoop")
+        e.replace("moo", "bar")
+        assert e.msg == "abarp"
+
 
 class uProxyError(libpry.AutoTree):
     def test_simple(self):
diff --git a/test/test_utils.py b/test/test_utils.py
index 2ff951d47..e22ec0391 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -137,6 +137,15 @@ class uHeaders(libpry.AutoTree):
         del self.hd["foo"]
         assert len(self.hd.lst) == 1
 
+    def test_replace(self):
+        self.hd.add("one", "two")
+        self.hd.add("two", "one")
+        assert self.hd.replace("one", "vun") == 2
+        assert self.hd.lst == [
+            ["vun", "two"],
+            ["two", "vun"],
+        ]
+
 
 class uisStringLike(libpry.AutoTree):
     def test_all(self):