diff -r e948154af406 Lib/test/test_bytes.py
--- a/Lib/test/test_bytes.py	Sat Apr 13 18:00:04 2013 +0300
+++ b/Lib/test/test_bytes.py	Sat Apr 13 16:33:46 2013 -0400
@@ -1211,6 +1211,28 @@
         self.assertRaises(TypeError, b.translate, None, None)
         self.assertRaises(TypeError, ba.translate, None, None)
 
+    def test_mtranslate(self):
+        rosetta = bytearray(range(0, 256))
+        rosetta[ord('o')] = ord('e')
+
+        ba = bytearray(b'hello')
+        ba.mtranslate(rosetta, b'l')
+        self.assertEqual(ba, b'hee')
+
+        ba = bytearray(b'hello')
+        ba.mtranslate(None, b'e')
+        self.assertEqual(ba, b'hllo')
+
+        ba = bytearray(b'ohio')
+        ba.mtranslate(rosetta)
+        self.assertEqual(ba, bytearray(b'ehie'))
+        
+        ba = bytearray(b'erie')
+        ba.mtranslate(rosetta, b'e')
+        self.assertEqual(ba, bytearray(b'ri'))
+
+        self.assertRaises(TypeError, ba.mtranslate, None, None)
+
     def test_split_bytearray(self):
         self.assertEqual(b'a b'.split(memoryview(b' ')), [b'a', b'b'])
 
diff -r e948154af406 Objects/bytearrayobject.c
--- a/Objects/bytearrayobject.c	Sat Apr 13 18:00:04 2013 +0300
+++ b/Objects/bytearrayobject.c	Sat Apr 13 16:33:46 2013 -0400
@@ -1417,6 +1417,100 @@
         return PyBool_FromLong(result);
 }
 
+PyDoc_STRVAR(mtranslate__doc__,
+"B.mtranslate(table[, deletechars]) -> bytearray\n\
+\n\
+Mutable translate performs the same action as translate,\n\
+in place on the string");
+
+static PyObject *
+bytearray_mtranslate(PyByteArrayObject *self, PyObject *args)
+{
+    register char *input, *target;
+    register const char *table;
+    register Py_ssize_t i, c;
+    PyObject *tableobj = NULL, *delobj = NULL;
+    Py_buffer vtable, vdel;
+    PyObject *input_obj = (PyObject*)self;
+    int inlen, outlen;
+    int trans_table[256];
+
+    if(!PyArg_UnpackTuple(args, "translate", 1, 2,
+                            &tableobj, &delobj)){
+        return NULL;
+    }
+
+    if (tableobj == Py_None) {
+        table = NULL;
+        tableobj = NULL;
+    } else if(_getbuffer(tableobj, &vtable) < 0) {
+        return NULL;
+    } else {
+        if(vtable.len != 256){
+            PyErr_SetString(PyExc_ValueError,
+                            "translation table must be 256 characters long");
+            PyBuffer_Release(&vtable);
+            return NULL;
+        }
+        table = (const char*)vtable.buf;
+    }
+
+    if (delobj != NULL) {
+        if (_getbuffer(delobj, &vdel) < 0) {
+            if (tableobj != NULL)
+                PyBuffer_Release(&vtable);
+            return NULL;
+        }
+    }
+    else {
+        vdel.buf = NULL;
+        vdel.len = 0;
+    }
+
+    inlen = PyByteArray_GET_SIZE(input_obj);
+    input = PyByteArray_AS_STRING(input_obj);
+
+    if(vdel.len == 0 && table != NULL){
+        for (i = inlen; --i >= 0; ) {
+            c = Py_CHARMASK(*input);
+            *input = table[c];
+            ++input;
+        }
+        goto done;
+    }
+
+    if (table == NULL) {
+        for (i = 0; i < 256; i++)
+            trans_table[i] = Py_CHARMASK(i);
+    } else {
+        for (i = 0; i < 256; i++)
+            trans_table[i] = Py_CHARMASK(table[i]);
+    }
+
+    for (i = 0; i < vdel.len; i++)
+        trans_table[(int) Py_CHARMASK( ((unsigned char*)vdel.buf)[i] )] = -1;
+
+    outlen = 0;
+    target = input;
+    for (i = inlen; --i >= 0; ) {
+        c = Py_CHARMASK(*input);
+        if (trans_table[c] != -1){
+            ++outlen;
+            *target++ = (char)trans_table[c];
+        }
+        ++input;
+    }
+
+    if(outlen != inlen)
+        PyByteArray_Resize(input_obj, outlen);
+
+done:
+    if (tableobj != NULL)
+        PyBuffer_Release(&vtable);
+    if (delobj != NULL)
+        PyBuffer_Release(&vdel);
+    return Py_None;
+}
 
 PyDoc_STRVAR(translate__doc__,
 "B.translate(table[, deletechars]) -> bytearray\n\
@@ -2874,6 +2968,8 @@
     {"lstrip", (PyCFunction)bytearray_lstrip, METH_VARARGS, lstrip__doc__},
     {"maketrans", (PyCFunction)bytearray_maketrans, METH_VARARGS|METH_STATIC,
      _Py_maketrans__doc__},
+    {"mtranslate", (PyCFunction)bytearray_mtranslate, METH_VARARGS,
+        mtranslate__doc__},
     {"partition", (PyCFunction)bytearray_partition, METH_O, partition__doc__},
     {"pop", (PyCFunction)bytearray_pop, METH_VARARGS, pop__doc__},
     {"remove", (PyCFunction)bytearray_remove, METH_O, remove__doc__},