Between 1971 and 1980, the senior one of us (C.S.R.) performed 101 primary total hip replacements in eighty-five consecutive patients who were less than fifty-five years old. All of the patients had degenerative joint disease. Survivorship analysis was used to calculate a predicted cumulative rate of success for this series of total hip replacements over ten years of follow-up. This method of analysis of the data was chosen because it provides a prediction of the expected durability of a total hip arthroplasty in any individual patient. The need for revision because of loosening or infection or else radiographic evidence of migration of a component was the criterion for failure. Two revisions were performed for aseptic loosening of the acetabular component. One infection necessitated revision, and radiographic evidence of loss of fixation was seen in one additional acetabular component and one femoral stem. Life-table calculations predicted that the survivorship of all of the total hip replacements in this series would be 87.6 per cent at ten years of follow-up. Based on the results of the application of this method of analysis to the current series, we concluded that a primary cemented total hip replacement, when performed for coxarthrosis, can be expected to function durably in an active middle-aged patient.