Fifteen patients had bilateral hip replacement with a porous-coated hip replacement in one hip and in the contralateral hip the same design, which had adjunctive hydroxyapatite coating on the porous coating. These patients were followed for an average of 6.5 years (range, 5-7.9 years). There was no difference in the clinical Harris Hip Scores between the two hips in these patients. The radiographic measurements did show improved bone remodeling in hips with adjunctive hydroxyapatite coating as measured by proximal cancellous hypertrophy and evidence of a buttress sign. The fixation of stems with hydroxyapatite coating showed fewer radiolucent lines (P = .013). The improved bone remodeling, which we had previously reported, has been maintained in these hips at intermediate-term follow-up and the fixation of the hydroxyapatite-coated stems is also now better. The results in these patients with bilateral hips, which allows complete control of the bone type, immunology, weight, activity, and age of the patient, suggests that the use of hydroxyapatite coating does provide improved fixation and the possibility of improved durability.