This study investigated changes in knee extensor and flexor strength of 17 mildly involved adolescents with cerebral palsy in response to an eight-week isokinetic strength-training program. Peak torque and work were used as strength outcome measures. Subsequent changes in gross motor function and walking efficiency were evaluated. The significant strength gains of 21 to 25 per cent observed were similar in magnitude to those previously reported for able-bodied individuals. A significant number of subjects showed an increase in gross motor ability. However, walking velocity and walking efficiency were unchanged. Strength gains of 15 to 17 per cent were maintained for three months after the cessation of isokinetic training.