We reviewed the results of treatment of sixteen patients who had had an isolated unilateral proximal femoral focal deficiency; nine were managed with a rotationplasty and seven, with a Syme amputation combined with an arthrodesis of the knee. We evaluated the perceived physical appearance, gross motor function, and metabolic energy expended in walking. The mean duration of follow-up was 9.9 years (range, four to fourteen years). The mean age of the patients at the time of the study was 13.9 years (range, eight to 18.4 years) in the rotationplasty group and 14.8 years (range, 9.5 to 19.9 years) in the Syme-amputation group. There were three female patients in each group. Roentgenograms showed that the femoral head was in the acetabulum (Aitken class A or B) in four of the seven patients in the Syme-amputation group and in five of the nine patients in the rotationplasty group; the remaining patients did not have this finding (Aitken class C or D). There was no difference in gross motor function or perceived physical appearance between the groups. Rotationplasty was associated with a more energy-efficient gait (mean, 0.153 milliliter of oxygen per kilogram-meter [range, 0.128 to 0.173 milliliter of oxygen per kilogram-meter] than was Syme amputation (mean, 0.169 milliliter of oxygen per kilogram-meter [range, 0.151 to 0.182 milliliter of oxygen per kilogram-meter]). Both types of treatment resulted in a net oxygen utilization per distance (efficiency) that was less than the values reported after amputations performed for non-congenital disorders.