Intraoperative fractures of the proximal femur occurred in 40 (38 patients) of 630 (6.3%) biological ingrowth total hip arthroplasties performed between January 1984 and July 1986. Twenty-three of these fractures occurred during 131 revision arthroplasties (17.6%) and 17 during 499 primary arthroplasties (3.5%). All but two of the fractures were recognized during surgery. Thirty-seven were treated with either Parham bands or cerclage wires. Bone graft was added to the fracture site in 31 fractures. All of the fractures healed. Three of the patients failed to achieve stable fixation and have required revision surgery. An additional patient has thigh pain with 2 mm of subsidence noted with serial roentgenographs. Femoral fractures can be prevented by preoperative templating of roentgenograms containing markers to measure magnification, routine overreaming of the femoral canal when implanting long-stemmed prostheses, and prophylactically applying wires or bands to femurs requiring the removal of screws.