Due to the improved prognosis of patients with primary malignant bone tumours, permanent attachment is also one of the problems encountered in the implantation of tumour endoprosthesis without bone cement, as surgeons are at present attempting to do in the case of conventional joint endoprostheses. The two methods which can be used for the cementless implantation of tumour endoprostheses are intramedullary stem fixation and extracortical attachment. Both methods require additional stabilisation by plates. Mechanical loading tests on 90 pairs of anatomical femurs showed that all the forms of attachment investigated exhibited adequate primary stability. However, it would appear necessary to fix two securing plates laterally and ventrally in order to achieve stable permanent attachment. The clinical results so far obtained with 18 cone endoprostheses and 12 stem endoprostheses are satisfactory. In the case of cone endoprostheses observed for an extended period after insertion, radiological checks showed the "incorporation" of the implant as an indication of stable permanent attachment. Radiological checks of patients with stem endoprostheses showed considerable structural movement in the area of the attachment. However, this did not result in signs of loosening so far. At the present time the cone attachment is preferable in view of the simpler operating technique involved and the more favourable radiological observations following the operation.