Objective: The aseptic loosening of the implants is the main contributor to the long-term failure of hip arthroplasty.One of the alternatives is to choose ceramic head instead of the traditional CoCr head. This study is conducted to determine the clinicalefficacy of a zirconia ceramic head. Methods: Twenty-six cementless total hip arthroplasties in 24 patients were performed using a zirconiahead coupled with polyethylene. All hips were followed for an average of 9 years (range, 6-13 years). A matched group of 26 hips in 26patients using cobalt-chrome heads coupled with polyethylene were also followed for average of 10 years (range, 5-14 years). The twogroups of patients were evaluated clinically and radiographically respectively. Results: The average scores of functional hip according toHarris standard improved from 46 (preoperatively) to 86 (at the final follow-up) in the Zirconia group, and from 50 to 88 in the CrCogroup. The mean liner wear rate of zirconia-polyethylene coupling was 0. 118 mm/year (range, 0. 064-0. 175 mm/year), and the linearwear rate of CrCo-polyethylene was 0.113 mm/year (range, 0.056-0.190 mm/year). There were 10 hips (27％) revised due to looseningor extensive osteolysis of the.cup in the Zirconia group, and only 4 hips (11.5％) in CrCo group. Conclusion: Results of the studysuggest that a zirconia ceramic femoral head has little advantage over a cobalt-chrome head in decreasing polyethylene wear in vivo. Ourstudy demonstrates that although changes in designs and materials may offer theoretical advantages over current components, their effectsremain questionable in vivo.