Extract - Gait analysis has radically changed the treatment of cerebral palsy. Preoperatively, it allows critical assessment of the specific pathologies of the patient. Postoperatively, it provides an accurate assessment of outcome. This assessment of outcome has in turn allowed the accurate critique of surgeries and has made it possible to discard treatments that are not useful or are perhaps even injurious. As a result of this continual reassessment of surgical techniques, several principals and insights have been learned. These include (1) the importance of re-establishing normal gait prerequisites, (2) the methods of reducing the energy expenditure of the pathologic gait, (3) the importance of skeletal structures in providing the lever arm by which muscles produce moments around joints, (4) the role and importance of two joint muscles, and (5) the importance of separating abnormalities, which are emanating from the neurologic lesion, from secondary ("coping") responses. Through gait analysis, it has become apparent that diplegia and hemiplegia are noninclusive terms, each of which contain a variety of homogenous patterns of gait. Eventually these patterns may be separated and identified and optimal treatment protocols for each pattern type developed.