Thirty-nine cementless hip arthroplasties using metal-on-metal articulation were consecutively implanted in 30 patients less than 50 years of age and compared with a matched control group (by age, diagnosis, Devane activity, and Harris hip scores) of cementless arthroplasties using ceramic-on-polyethylene articulation. The Harris hip score at follow-up (minimum 5 years) for the metal-on-metal was 94.9 (range, 74-100). After the same follow-up, the results of the ceramic-on-polyethylene were significantly worse: 9 osteolyses and 7 surgical revisions related to wear (none in the metal-on-metal). Five-year survival rates were 97% +/-2% for the ceramic-on-polyethylene and 100% for the metal-on-metal. The metal-on-metal may be recommended to prevent wear problems in younger and more active patients; however, a longer follow-up is required to confirm this encouraging data.