Four hundred arthroplasties with the Bateman (or universal) prosthesis were performed from June 1974 to January 1985, including 286 cases with osteoarthritis (OA) and 114 with rheumatoid arthritis (RA). Evaluation was made according to the d'Aubigne-Postel method. The follow-up period was from three to 14 years, with an average duration of eight years, five months. The results were excellent in 230 cases (172 OA, 58 RA), good in 140 (98 OA, 42 RA), fair in eight (four OA, four RA), and poor in 22 (12 OA, ten RA). Radiolucencies were present in the femoral side in 25%. Radiolucency of more than 2 mm was seen in 20 cases (5%). The complications were six cases of fracture of the plastic insert, four cases of protrusio of the acetabulum, four dislocations, eight cases of loosening of the femoral stem, one deep infection, two superficial infections, 15 cases of thrombophlebitis, one pulmonary embolism, and one death. A careful analysis of these complications and a discussion of their treatment are presented. Reoperations were performed in 20 patients (5%). The universal arthroplasty appears to be a safe and reliable procedure.