The surgical procedure is a selective dorsal rhizotomy. Physical therapy (PT) includes passive and active range of motion, facilitation of isolated muscle control, transitional movements, strengthening, transfer skills, and gait training. The PT schedule is 2-hour sessions 5 days a week for 1 month, 1-hour sessions 5 days a week for 5 months, then a standard therapy program for the remainder of the study (total of 6 months). Parents supervise exercise on non-PT days.