The records of all patients who had had a total hip replacement complicated to a fracture of the ipsilateral femur in the intraoperative or postoperative period were collected from six London and Toronto teaching hospitals. Thirty-five patients (thirty-seven fractures) were studied to determine the effects of the fracture on the total hip replacement. The results of the total hip replacement ultimately were rated as satisfactory in fourteen patients (40 per cent) and unsatisfactory in twenty-one patients (60 per cent). Our study suggests that fractures proximal to the tip of the prosthetic stem that occur postoperatively should be treated conservatively if the prosthesis is intact. If subsequent symptomatic loosening develops, a revision can be done after the fracture has healed. Intraoperative fractures that occur proximal to the tip of the prosthesis and all fractures occurring at or distal to the tip should be stabilized surgically. The best results were obtained using a long-stem prosthesis supplemented with internal fixation of the fracture. If rigid fixation is not achieved at surgery, postoperative immobilization is required. Fractures entirely distal to the tip of the prosthesis do not result in prosthetic loosening and may be treated in a routine fashion if care is taken to avoid unnecessary areas of stress concentration.