Seventeen patients with diplegic cerebral palsy were assessed by clinical examination and three-dimensional gait analysis before and after surgery to improve gait. Selection of surgical procedures was according to a fixed set of selection criteria. The average postoperative follow-up was 3.8 years (range, 2.6-5.7 years). Clinical examination revealed an improved range of motion for the ankle and no reduction in the power grade at the hip, knee and ankle after surgery. Kinematic parameters showed improved knee extension in stance and significant changes towards a normal ankle motion pattern postoperatively. Kinetic evaluation demonstrated that most of the total power during walking was generated at the hip, with the ankle contributing a small part. After surgery, patients walked faster with an increased power generation at the hip during first double support and at the ankle during push off. Power generation at the hip in stance is pointed out to be an important mechanism for propulsion during walking.