The cement-free hip prosthesis coated with hydroxyapatite was developed to obtain primary firm fixation by an enhanced anatomic design and secondary biologic stable fixation by hydroxyapatite which is bioactive and has the same chemical and structural components with those of human bone tissue in total hip arthroplasty. Between January 1992 and June 1994, we used ABG cement free hip prosthesis (Anatomique Benoist Giraud, Howmedica Europe, Staines, England) in 28 hips (avascular necrosis of femoral head; 17, osteoarthritis; 6, posttraumatic arthritis; 3, rheumatoid arthritis; 2) of 25 patients in Pusan National University Hospital. Those cases had a minimum of two years and maximum of four years and five months (average three years and six months) of follow up, including analysis of the clinical and radiological data. The results were obtained as follows: 1. The average Modified Harris Hip Score increased from 51 points preoperatively to 96 points at last follow up. Almost all cases (97%) were excellent or good results in Modified Harris Hip Score. 2. In radiologic results, no migration of the cup, no change in the inclination of the cup, ar.d no oste-olysis around the cup and the stem were observed. Endosteal bone apposition around the cup was found in 54% of the cases and subcortical cancellous densification around the stem was found in 89%. This results indicate that we obtained direct and biologic firm fixation without fibrous tissue interposition between bone and metallic component by inducing on-growth of bone. 3. In the radiologic follow up according to the initial bone quality, it was demonstrated that the incidences of cortical hypertrophy, calcar resorption, and radiolucent line in type B and type C were higher than those in type A. The early clinical and radiological results of the cement-free hip prosthesis coated with hydroxyapatite are encouraging, although a longer follow up period is necessary.