The results of conservative and operative treatment of dislocated fractures of the acetabulum are compared. The types of fracture are described where surgical stabilisation is indicated. Depending of the type of fracture, the causes of unsatisfactory results following operative treatment are: primary lesions of the cartilage, difficulties with reduction and retention, septic complications. The aim of surgery is first of all the anatomic reconstruction of the supporting area of the acetabulum. 2/3 of our patients were operated between the 2nd and the 14th day. The lateral position with the extremity freely movable is recommended for dorsal and lateral approach. A trochanter traction screw with extension facilitates the operative reduction. It was possible to re-examine 45 of 64 cases after a period of between 2 and 13 years. Results were evaluated according to the scheme by Merle d'Aubigné. 35 patients had very good or good results, in 3 cases secondary arthrodesis was necessary and in one case a total hip prosthesis was implanted. Dislocated acetabular fractures should be be operated as soon as possible if conservative methods fail. Late reconstruction may also be successful. The lesion of the sciatic nerve is an absolute indication for operation. Satisfactory results can be achieved by anatomic reconstruction even in cases with multiple fragmentation.