Intravascular nephroblastoma involving the renal veins or inferior vena cava, occurring in 6 to 10 per cent of the cases, dramatically complicates the treatment course for those individuals. Heroic surgical procedures, including sternal splitting and cardiopulmonary bypass, have been used to treat these tumors, often with an added morbidity and increased mortality. We have detailed the dramatic responses to preoperative chemotherapy in 3 patients with intravascular nephroblastoma, which resulted in either complete eradication or marked shrinkage of the intravascular tumor, greatly simplifying the ensuing surgical procedure. These observations strongly indicate that preoperative chemotherapy should be used as the primary treatment in patients with this condition.