Flexor spasticity is common in the upper extremity after insult to the central nervous system. This leads to decreased function and hygiene problems as a result of the inability to extend the fingers. The results of fractional lengthening of the finger flexors of 27 patients with upper extremity flexor spasticity of the finger flexors were examined. Patients were divided preoperatively into those with potentially functional hands and those who were nonfunctional based on the presence of motor control and hand sensibility. Follow-up time averaged 33 months. Postoperatively, all five nonfunctional hands, which lacked any motor control, improved in posture, and the hygiene problems resolved. Twenty of the 22 patients with potentially functional hands (91%) improved their spastic hand function score, a mean of 3.7 points. Two patients (9%) decreased their spastic hand function score as a result of overlengthening of the finger flexors, with loss of grip strength.