Abstract
A common peroneal nerve palsy caused by a ganglion cyst is a rare entity. A 48-year old man was referred with a six year history of intermittent pain that had resulted in a complete palsy of the common peroneal nerve. A magnetic resonance (MR) scan showed compression of the nerve by a ganglion, which was excised and the nerve was released. Three months later the lost muscle function had returned completely.