Over a period of 2 years pre-operative embolization of the renal artery was carried out according to the method of Gianturco, which offers certain advantages over other methods of embolization, in 25 patients with renal tumours. The most important aims of pre-operative embolization of the renal artery were considered to be to prevent tumour cells from being flooded out and to be able to ligate the vena renalis first. Because of the clinical reaction to be expected the embolization should be performed immediately before the operation, which still allows the aims to be achieved. In our opinion embolization cannot replace pre-operative irradiation.