The aim of this study was to assess the effect of partial body weight support on the oxygen cost of treadmill walking in children and adolescents with spastic cerebral palsy (CP). Five children and adolescents (2 girls and 3 boys) with spastic CP (12.4 ± 3.6 years) volunteered for the study. Participants performed three 4-min tread mill walks on three separate days at their comfortable treadmill walking speeds. At each visit a different partial body weight harness setting was used. Significant (p < .05) differences in oxygen cost were found when the harness was worn but not connected to the support frame. Partial body weight support reduces the oxygen cost of walking in children and adolescents with spastic CP.