This report describes four infants with hepatic hemangioendotheliomas and cardiac failure who had extensive portal venous and systemic collateral arterial supply complicating hepatic arterial embolization. One patient with diffuse hepatic hemangioendothelioma and extensive portal vein supply but minimal systemic collateral arteries showed no improvement after technically successful hepatic artery embolization and died with disseminated intravascular coagulation and sepsis. A second infant with extensive portal vein and collateral supply died without undergoing embolization. Two patients had portal vein-hepatic vein fistulas as well as an extensive systemic arterial supply. Both infants tolerated staged hepatic and collateral artery embolization, although one patient died of congestive heart failure, probably related to pulmonary hemangiomas. The authors conclude that angiographic study of the potential collateral vessels and portal venous circulation should be performed before embolization. Patients with shunting from the portal vein to the hepatic vein and minimal systemic arterial collateral circulation should not undergo hepatic artery embolization.