Fourteen dogs were subjected to two methods of producing roentgen-guided renal infarction. In each dog in one group of nine dogs, a single balloon catheter in the renal artery and the injection of a mixture of Sephadex G-50 and tantalum pentoxide resulted in nearly complete renal infarction; a satisfactory result was obtained in seven dogs. In each of five dogs, a double-catheter technique was used, with a balloon catheter inflated in the abdominal aorta after inserting a catheter into the renal artery. Only two dogs showed satisfactory results from this experiment, and it was abandoned in favor of the former technique. The experiment is to be continued, refining the balloon catheter to be placed in the renal artery, and with the intention of adding thrombin to the mixture of Sephadex and tantalum pentoxide.