Resection of a Wilms' tumor that extends into the vena cava or right atrium results in excellent survival when combined with adjuvant therapy. Preoperative identification of the presence of intravascular tumor thrombus and the level of vascular involvement is essential. It facilitates safe surgical resection, with cardiopulmonary bypass immediately available for retrohepatic and atrial tumors. Six patients with intracaval or intracardiac tumor thrombus were treated over a 5-year period with no perioperative deaths. Preoperative chemotherapy was useful in two patients with extensive tumors and pulmonary metastases. Our results using an integrated management plan suggest that an aggressive surgical approach is justified for this extensive variant of Wilms' tumor.