The hip joint forces of sheep and dogs were measured with instrumented endoprostheses and the results were compared with reported data concerning these forces in man. In all animals load directions with 0 to 30° inclinations relative to the femoral axis predominated. The transverse components mostly acted from medio-ventral directions. While the force orientations varied little during each single stance phase, they changed rapidly during the swing phase. Strong inter-and intra-individual differences of load directions were found in all animals. Irregular forces, acting upwards or transverse to the femur, were frequently observed. Maximum joint forces were up to 110% of body weight and depended more on the postoperative time than on the walking speed. Load orientations in the animals were similar to those reported for man. In this regard sheep and dogs appear equally well suited for tests of hip endoprostheses for man.