The recent increase in popularity of selective posterior rhizotomy demands objective documentation of surgical outcome. For this reason, the authors have analyzed the status of 25 children with spastic cerebral palsy before and after rhizotomy to determine the effects of this therapy on muscle tone, range of movement, and motor function. Postoperative tests showed a reduction in muscle tone compared with preoperative assessments. Range of motion in the lower extremities was significantly increased and improvements in functional gross motor skills were noted. An increase in range of motion in the knees and thighs during gait was detected in 18 ambulatory patients studied with computerized two-dimensional motion analysis. Preliminary findings indicate that selective posterior rhizotomy reduced spasticity, thereby increasing range of motion and contributing to improvements in active functional mobility.