Forty-nine cemented total hip arthroplasties in patients younger than 45 years were reviewed, with an average follow-up period of 16.2 years. The results were compared with the same group previously reported at average follow-up periods of 4.5 and 9.2 years. Clinically satisfactory results were 27% at 16.2 years compared with 78% at 4.5 years and 58% at 9.2 years. The revision rate increased from 12% at 4.5 years to 33% at 9.2 years to 67% in this study. The revision rate for patients younger than 30 at the time of the index arthroplasty was 82% compared with 56% for those over 30. Impending failure was present in 81% of the 16 unrevised hips compared with 56% at 9.2 years and 29% at 4.5 years. Patients younger than 30, in Charnley category A or B, and with a diagnosis of osteonecrosis or osteoarthritis had the poorest clinical results. As in the previous two studies, the best results were obtained in category C patients who were over 30 years of age with inflammatory collagen disease. The purpose of this study is to report the long-term (average, 16.2 years) follow-up results of patients under the age of 45 who underwent cemented total hip arthroplasty at Rancho Los Amigos Medical Center between 1972 and 1978. The 4.5-year and 9.2-year results form the basis for comparison.