We studied the cases of eighty-one patients (108 total hip arthroplasties), ranging in age from fourteen to forty-five years, at an average of 4.5 years after the index operation and evaluated them with regard to six major factors: age, disease, Charnley category, prior operations, length of time since arthroplasty, and quality of the arthroplasty with regard to cementing technique and component position. After two to five years 78 per cent were satisfactory, but after five years or more only 72 per cent were satisfactory. Patients who were less than thirty years old had poorer results. Good technique yielded 93 per cent satisfactory clinical results. The patients in this study with the worst prognosis for success following total hip arthroplasty were less than thirty years old, had osteonecrosis or osteoarthritis as the primary disease, and had a less than optimum reconstruction. Patients who were alcohol-abusers or who had had a prior hip infection or a prior acetabular cup or femoral hemiarthroplasty also had a poor prognosis. Patients who had the arthroplasty for collagen disease or were thirty years old or older, or both, and had a good technical reconstruction had the best prognosis.