Cerebral arteriovenous fistula may cause a significant increase in cardiac output. So far, the right ventricular output measurement with conventional cardiac output methods has been difficult in newborn infants because of the shunts through the foramen ovale and patent ductus arteriosus. This difficulty can be avoided by measuring left ventricular output with the pulsed Doppler ultrasound method. In our case, the patient was a newborn infant with large patent ductus arteriosus and an arteriovenous malformation of the great cerebral vein of Galen. The malformation was found by noticing a loud murmur from the infant's head. The diagnosis was later confirmed by ultrasound scanning and a computer tomography. Left ventricular output was enormous with values from 740 to 830 ml/min/kg, when the normal value for the newborn infant at this age is 260 ml/min/kg. Because of constant cardiac failure, the malformation was operated on. The infant died of cardiac failure during this operation. An enormous left ventricle output in an infant with arteriovenous fistula and patent ductus arteriosus predisposes to cardiac failure. The Doppler ultrasound method in newborn infants seems to be a useful tool to determine cardiac function.