Today, alloarthroplasty is one of the many standard therapeutical procedures in osteoarthrosis of the hip, or coxarthrosis. With this operation, many patients can be completely relieved from pain and regain their ability to walk to an excellent degree. However, long-term observations have shown that the stability of the prostheses does not always correlate with the life expectation of the operated patient. Dislocations and states of irritation, over and above infections, may necessitate repeat surgery. It must be borne in mind that such repeated operations are by no means certain to produce safe results. Hence, it is recommended to employ for the first implantation a prosthesis model which offers a better chance of interchangeability. This possibility is supplied by the double-cup prosthesis of the type described by Wagner and other authors. Certain limitations are imposed by the prosthetic form and by the surgical approach; these limitations should be taken into account when choosing the double-cup prosthesis.