The results of reconstruction with 3 standard knee joint endoprostheses in advanced gonarthrosis are reported prospectively for 111 consecutive cases operated upon during the years 1973 through 1977 according to a consecutive, precise routine. High tibial osteotomy was indicated in the early stages of the disease, i.e., roentgenographic Grades I and II. In advanced gonarthrosis constituting Grades III to V, unicompartmental reconstruction with hemiprosthesis was performed in 68% of the cases, while 26% needed a stablizing total surface prosthesis and 6% a hinge prosthesis. This differentiation is important in view of the better results achieved in the category of hemiprosthetic reconstructions compared with those of the 2 latter categories. In the total series, 96% of the patients were satisfied or improved correlating with the clinical assessments made at regular clinical and roentgenological examinations 1 to 5 years after the operation; there were 99% in the hemiprosthetic group and 93% in the group having total surface replacement. In the former group of patients, wear of the tibial component was detected in 3%, while loosening occurred in 6 and 11%, respectively. The rates of primary deep infection were 1 and 3%, respectively, and, in addition, 7% (3 cases) in the latter group showed the occurrence of late deep infection. Relief of pain, correction of deformity and a range of movement of 90 degrees or more, were the most significant results. Strict indications and operative techniques should be used according to the different stages of gonarthrosis.