Vessel malformations, which are very rare, can be diagnosed prenatally using color Doppler sonography. We present a case of a fetus which, at first prenatal presentation at 27 weeks, was diagnosed as having an intrapulmonary arteriovenous malformation. On the basis of the gray-scale sonographic findings of cardiomegaly and dilatation of the right pulmonary vein and right pulmonary artery, color Doppler sonography was performed which identified an arteriovenous malformation of the right lung. By means of pulsed Doppler sonography it was possible to determine the hyperdynamic blood circulation in the incoming and outgoing vessels of the vascular malformation: right pulmonary artery peak systolic velocity = 90 cm/s and end-diastolic velocity = 30 cm/s; right pulmonary vein peak systolic velocity = 60 cm/s and end-diastolic velocity = 30 cm/s. The fetus went on to develop hydrops as the result of an arteriovenous valve insufficiency. At 30 weeks' gestation a Cesarean section was performed and the neonate died due to respiratory and hemodynamic problems during catheter insertion. The autopsy provided pathoanatomical confirmation of the prenatal diagnosis of an arteriovenous malformation of the right lung. There was no evidence of hereditary hemorrhagic telangiectasia.