In hydranencephaly, the cerebral hemispheres are absent or represented by membranous sacs with remnants of frontal, temporal or occipital cortex dispersed over the membrane. The brain stem is relatively intact. The cause of hydranencephaly is unknown, but bilateral occlusion of the internal carotid arteries during early fetal development can explain most of the pathologic abnormalities. We evaluated a case of hydranencephaly by magnetic resonance (MR) angiography. MR angiography shows both common, external carotid and vertebrobasilar arteries with no delineation of both internal carotid arteries from their origins. A brief review of the related literature was given on this subject.