Abstract
A case of regression of a renal carcinoma involving the inferior vena carva is presented. After 6 weeks of radiation therapy there was considerable diminution in the size of the tumor, rendering its surgical excision amenable. The tumor thrombus in the inferior vena cava also was markedly diminished after 5,000 rads. Radiation therapy is a valuable tool in the primary or adjunctive treatment of renal cell carcinoma. Preoperative treatment should be considered with large tumors and vena cava involvement.