The tarsal tunnel syndrome is not as commonly diagnosed as is its counterpart in the hand, the carpal tunnel syndrome. Electrodiagnostic evaluation has shown that reduced amplitude and increased duration of motor evoked potentials are more sensitive indicators of the presence of tarsal tunnel syndrome than is the distal motor latency. The lateral plantar branch of the posterior tibial nerve is probably affected earlier than is the nerve's medial plantar branch. Surgical release usually results in complete relief of the compression neuropathy. Electrodiagnostic evaluation also may help to separate patients with a tarsal tunnel syndrome from those with compression of the first sacral-nerve root.