Release of the transverse carpal ligament is a highly successful treatment for the majority of patients with carpal tunnel syndrome. However, carpal tunnel syndrome may also be caused by space-occupying lesions within the carpal canal that compress the median nerve. In these cases, simple release of the transverse We describe a patient with carpal tunnel syndrome whose symptoms were not relieved by simple transverse carpal ligament release. Subsequent surgery revealed a lipoma of the flexor tendon sheath.