A prospective clinical study was done for quantitative examination of motion of the hip, gait, and proximal femoral remodeling after in situ fixation of a slipped capital femoral epiphysis. In situ fixation was performed in forty-five consecutively treated patients (fifty-six hips). Thirty-nine (87 per cent) of the patients returned for examination two years after treatment. The greatest percentage of motion of the hip returned within six months after treatment. Despite loss of internal rotation of the hip, the mean foot-progression angle was 10.8 degrees. Radiography and computerized tomographic scanning revealed minimum change in the relationship of the femoral head to the femoral shaft and no change in the neck-shaft angle. Motion returned despite minimum osseous remodeling. The early return of motion (in the first three months) may have been due to relief of pain, spasm, and synovitis, while soft-tissue stretching and resorption of bone in the anterolateral part of the femoral neck may have accounted for the remainder of the increase in internal rotation.