The results of 100 primary arthroplasties with a porous-coated anatomic total hip prosthesis that were performed consecutively in ninety-one patients were followed prospectively for five to seven years after the operation or until death. Clinical Harris hip ratings and anteroposterior and lateral radiographs were made preoperatively, several times in the first postoperative year, and at annual intervals thereafter. Average sequential hip ratings were maintained between 92 and 93 points during the follow-up interval. Pain in the thigh, which did not limit function, was recorded at the yearly examinations from the first to the fifth year. After one year, 18 per cent of the thighs were painful, and in succeeding years, 19 per cent, 23 per cent, 26 per cent, and 15 per cent were painful. Radiographs demonstrated that the fixation of the femoral component was by ingrowth of bone in 94 per cent of the hips, by stable fibrous fixation in 1 per cent, and by unstable fibrous fixation in 5 per cent, according to the criteria of Engh et al. By five years, 6 per cent of the acetabular components had migrated, and 5 per cent of the femoral components had subsided. Two acetabular components had been revised, and one revision of a femoral component was pending. The evaluated device was an early-generation prosthesis that was designed for insertion without the use of cement. Further study is necessary to determine the long-term durability of the prosthesis-bone interface.