Arterial embolisation of renal tumours with foreign particles is described. This involves occlusion of the arteries supplying the tumour through a catheter introduced by the trans-femoral route. Pre-operative and therapeutic embolisation should be distinguished. During pre-operative embolisation, the kidney should be totally occluded by the foreign particles in order to obtain a bloodless operation zone and in order to avoid the much feared production of tumour emboli. Because of the clinical consequences of renal artery emboli, this procedure should be carried out immediately before the operation. During therapeutic embolisation, which is not followed by an operation, only those vessels supplying the tumour should be occluded in order to avoid the complications of a renal embolus. Ischemia of the tumour and less rapid growth may then be excluded.