Five cases of heart failure, resulting from a cerebral arteriovenous fistula and aneurysm of the great vein of Galen, are reported. In two infants the diagnosis was made roentgenographically; one improved after arterial ligation. In four cases, autopsy demonstrated the anomalous vessels and dilatation or hypertrophy of the heart. In three cases there was spongy necrosis of the brain. The pathogenesis of heart failure seems to be related to an enormous increase of the intake of the right atrium and ventricle. The cerebral damage seems to be due to ischemia caused by shunting of blood toward the veins bypassing the capillary network. Early diagnosis can be made by auscultation of the head and cerebral arteriography in infants who develop heart failure. Treatment is discussed.