Aneurysms of the vein of Galen are rare, representing less than 1% of all intracranial arteriovenous malformations. In the fetus, however, almost all cerebral arterial malformations involve the vein of Galen, usually presenting in the neonatal period with severe cardiac failure leading to neonatal death. In this report we present a case of arteriovenous malformation involving the vein of Galen detected prenatally at 3.5 weeks with the use of color Doppler ultrasonogvaphy. The literature is reviewed in an attempt to delineate the vole of prenatal ultrasonography in the diagnosis and its impact on perinatal outcome. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology