In a prospective study, the authors used a porous tantalum monoblock acetabular component for primary total hip arthroplasty between November 1997 and June 1999. A total of 156 consecutive primary total hip arthroplasty were done in 143 patients younger than 75 years. A total of 151 hips had a follow-up time from 8 to 10 years. The average preoperative total Harris hip score of 44.0 +/- 13.8 increased to 97.0 +/- 6.2 at the latest follow-up. The average preoperative Oxford hip score of 43.3 +/- 6.5 improved to 13.9 +/- 2.3 at the latest follow-up. Radiographic evaluation including the Ein-Bild-Röntgen-Analyse (EBRA) digital system showed no radiographic evidence of gross polyethylene wear, progressive radiolucencies, osteolytic lesions, acetabular fracture, or component subsidence. There were 7 (4.5%) postoperative complications all unrelated to the acetabular component.