After excision of the hemipelvis through a combined subnatal and anterior incision preserving the lower extremity, five patients with periacetabular chondrosarcoma, after a follow-up of three to six years, were able to walk with no support or with minimum lateral support and had resumed their preoperative occupations. None had either the instability that might have been anticipated or incapacitating discomfort from the neoarthrosis, and there was no evidence of spread or recurrence of tumor in any of the five patients. The procedure, which has the same basic indications as a hindquarter amputation, is a rewarding substitute for that mutilating operation, although the follow-up is too short and the series is too small to warrant conclusions as to the cure rate.