To evaluate the effect of hydroxyapatite coating on cementless femoral stem, a prospective randomized clinical trial was conducted. A total of 84 hips from 69 patients were assigned to a hydroxyapatite/tricalcium-phosphate-coated group or a noncoated group. Thirty-two patients (37 hips) who received hydroxyapatite/tricalcium-phosphate-coated stems and 31 patients (38 hips) who received noncoated stems were followed for an average of 127 months. Forty-nine patients (78%) were men, and the average age was 45.5 years. Preoperative diagnosis was osteonecrosis in 62 hips (83%). The mean Harris hip score at the time of final follow-up was 91 points in the coated group and 90 points in the noncoated group. Six acetabular components (3 in each group) were revised. One femoral stem in the noncoated group was loose. There was no statistical difference in the survival distributions of the implants between the 2 groups.