Total hip arthroplasties in patients younger than 45 years. A nine- to ten-year follow-up study. Eighty-one cemented total hip arthroplasties in patients younger than 45 years were reviewed with an average 9.2-year follow-up interval. The results were compared with the same group previously reported at an average follow-up time of 4.5 years. Clinically satisfactory results were 58% compared with 78% at 4.5 years. The revision rate almost tripled to 33%. Impending failure was present in 56% of those hips not yet revised. In the first study, technique was a primary determinant of success. In this report there was no influence of technique on the incidence of revision. Age did not influence revision rates either, with 35% in patients younger than 30 years and 32% in patients aged 30-45 years. Patients younger than 30 years had fewer satisfactory clinical results and a higher rate of impending failure. As in the first study, the best results were obtained in patients with inflammatory collagen disease aged from 30 to 45 years. 