Thirty-six hands in thirty-two patients had internal neurolysis of the median nerve and carpal tunnel release for severe carpal-tunnel syndrome. Median-nerve function was evaluated in all hands using Weber two-point discrimination and electromyography. Thenar-muscle strength or bulk, or both, were recorded in thirty hands. Ten hands also had Semmes-Weinstein monofilament pressure-testing. The indication for neurolysis in these selected patients was the presence of any one of the following: an increase in two-point-discrimination values, thenar-muscle atrophy, or denervation potentials in the thenar muscles. Twenty-two (76 per cent) of the twenty-nine hands that had had diminished two-point discrimination preoperatively regained normal sensibility. Seven (70 per cent) of ten hands that had had thenar-muscle weakness (grade 3 or less) preoperatively regained grade-4 or 5 strength. Nine (50 per cent) of eighteen hands that had had thenar-muscle atrophy regained normal muscle bulk. Seventy-six per cent of the patients in this series recovered sensation and 70 per cent recovered muscle strength, and the procedure was well tolerated. Although no studies comparing the results of treatment of severe carpal-tunnel syndrome with and without internal neurolysis have been reported, we think that neurolysis, if it is done by a surgeon who is skilled in microsurgery, is a safe and effective procedure for severe carpal-tunnel syndrome.