In the last six years the authors have implanted 340 hip joint prostheses of the Zweymüller/Endler or Zweymüller type in 285 patients from the lateral transgluteal approach. Approximately one-third of these patients (111) had previously undergone surgery on the hip joint in question. Intraoperative complications included four cases of elongation of the leg due to implantation of an over-long prosthesis shaft. Four of the shafts implanted were too small and in two cases subsequently loosened. In two patients a divulsion of the trochanter major occurred and there were two cases of cracking of the calcar femoris with involvement of the trochanter minor. There were also two cases of shaft divulsion at the level of the prosthesis tip. Postoperative complications included periarticular ossifications in 41 cases. There were 11 cases of phlebothrombosis and six of pneumonia. Superficial hematomas developed in the wound region in four cases. In addition, there were two cases of shaft and one of acetabular loosening, as well as three prosthesis dislocations. Between October and December 1987, a total of 232 of these patients were examined and the results rated according to Merl d'Aubigne's classification: 166 (71%) were classified as very good or good, 49 (21%) as satisfactory, and 17 (7%) as unsatisfactory. The most common postoperative complication was periarticular ossification, seen in 41 cases. Even though this is not a serious complication and the periarticular ossifications did not necessarily result in severe limitation of movement, a major functional loss as compared to the preoperative findings was seen in the patients with severe ossification (IIIrd degree) at the examination 12 months postoperatively. By giving EHDP, since November 1984, it has proved possible to reduce the incidence of periarticular ossifications from 28 to 12%. In the last 24 months even better results have been achieved by administration of EHDP unter function-scintigraphic control. According to the author's results the Zweymüller/Endler and Zweymüller systems satisfy the requirements for a cement-free total hip replacement since, on the one hand, intraoperative and postoperative complications are slight and, on the other, a good functional result is achieved. The Zweymüller prosthesis has proved particularly suitable for hip joints operated on previously.