Hypernephroid carcinoma of the kidney, more frequently than any other tumor, may spread into the inferior vena cava by direct extension of a tumor-thrombus, may fill this vessel almost completely and in rare instances may penetrate the cavities of the right atrium and ventricle. In the most recent review, Polayes and Taft1found eleven cases in which such a tumor-thrombus of renal origin had invaded the heart in this manner, and they added a case of their own. Of these twelve cases, five presented the tumor-thrombus extending into both atrium and ventricle, while in the remaining cases the atrium alone was involved. Most of these cases have been characterized clinically by slow, insidious onset with edema of the lower extremities, hematuria, enlarged liver, jaundice, and ascites in the late stage. The case reported here is of interest because of the large size of the tumor-thrombus in the right ventricle