Since 1988, metal-on-metal articulation from cobalt-chromium-molybdenum alloy was reintroduced into hip arthroplasty as an alternative to metal-on-polyethylene or ceramic-on-polyethylene components. Modular joint surfaces were developed for the second generation metal-on-metal articulation using newly introduced and proven prosthetic implants. Since 1990, 78 patients with 78 uncemented total hip replacements were followed up in a prospective study. The mean followup was 60 months. Three patients were lost to followup. The average age of the patients at the time of surgery was 48.8 years. Thirty-three patients had been operated on previously. No early infections occurred; one late infection occurred after 3 years. Dislocation of the prosthesis occurred in one patient who was lost to followup. In two patients ectopic ossifications were removed 17 and 27 months postoperatively. At revision surgery no metallosis could be identified. At the last followup examination, the Harris hip score was 96.8 points on average. There was no evidence that the metal-on-metal articulation gave rise to new problems or complications. Metal-on-metal articulation reduced wear considerably in the authors' previous experience. It is hoped that foreign body reactions are reduced significantly so that an alternative for total hip replacement in younger and active patients will be available.