Total hip replacement arthroplasty has become an established procedure in the management of painful arthritic hip in past two decades. However there is no many reports that concern follow-up study in total hip replacement arthropiasty. This is a follow-up study in 100 total hip replacement arthroplastics in 86 patients of 157 total hip replacement arthroplasties in 135 patients, performed at the Department of Orthopedic Surgery, Seoul National University Hospital, between November 1973 and December 1979. The longest fallow-up was 5 years and the shortest 6 months, the average being 2 years and 6 months. 1. There were 54 males (63%) and 32 females (37%). 2. The underlying diseases of 100 hips were avascular necrosis of 35 hips, septic hip residua of 31 hips, primary osteoarthritis of 9 hips, old hip fracture of 9 hips, Legg-Perthes disease of 7 hips, rheumatoid arthritis of 5 hips, congenital dislocation of 3 hips, and failed endoprosthesis of 1 hip. 3. The types of prosthesis used were Muller ones in 82 hips, T-28 in 17 hips, and Charniey and Harris type one case respectively. 4. In the half cases of a hundred total hip replacement arthroplasties, the anterolateral or posterolateral approach was used without trochanteric osteotomy. 5. Postoperative complications were as follows: 13 cases of wound problem including 3 early deep infections, 2 dislocations, 1 femoral nerve palsy, 3 peroneal nerve palsies, 1 acetabular perforation, 2 femoral shaft perforations, 14 trochanteric problems including 11 cases of wire breakage, 2 nonunions, and 3 cases of trochanteric bursitis 3 ectopic ossifications, 3 cases of radiological loosening including 2 femoral and 1 acetabular. 6. The range of motion were improved from 28 to 5 of flexion contracture, from 91 to 101 of further . flexion, and from 16 to 48 of abduction in the average. 7. The improved ranges of motion were varied with disease group rather than type of prosthesis and the length of neck of prosthesis. 8. The function of each hip was evaluated preoperatively and postoperatively by the method of Harris and d'Aubigne, and improved from 55.3 and to 88.2 by Harris score and from 11.2 to 15.8 d Aubigne respectively.