Two unusual cases described here are unique in that they are both involved with a large bulbous degenerative pseudotumorous swelling of the peroneus brevis tendon, one with some synovitis and cystic swelling, the other without synovitis. The second occurred apparently as the result of recreational strain. In neither case was there enlargement of the peroneal tubercle or stenosis of the sheath. The enlargement in both cases was such that simple release of the retinaculum did not seem sufficient and excision of the entire pseudotumorous swelling of the peroneus brevis tendon was necessary. The peroneus longus was not involved in either case.