The risk of fatal hemorrhage may limit the completeness of resection in hepatic malignancies and in vascular extensions of Wilms' tumors. We have used Ein's technique of deep hypothermia (average 17 degrees C) with cardiac arrest (average 39 minutes) and exsanguination in performing five hepatic and two intravenous Wilms' tumor resections. The initial hepatic resection takes less than 15 minutes to perform in a bloodless field and the specimen is immediately examined by frozen section for determination of adequacy of margin. Additional resection is easily performed. Of four trisegmentectomies and one left lobectomy, two required additional resections. Mattress sutures were used to control hemorrhage during recirculation. One patient died from bleeding and cardiac decompensation and another from recurrence of tumor. The Wilms' tumors extended from the iliac vein into the right atrium in one child and from the right renal vein to the right atrium with extensions into the hepatic and lumbar veins in another. After nephrectomy, the atria and inferior vena cava were opened and the tumor extracted under direct vision. Both patients are well.