The study of six patients with hydranencephaly is reported. Clinical and necroscopic findings have been performed in correlation to routine laboratory examination. The Authors have concluded that transilumination is an important procedure for early diagnostic of these cases, especially when the patients have a milder or incomplete form of the syndrome. The necroscopic findings suggest that hydranencephaly may be the result of encephaloclastic lesions (inflammatory, mechanical or vascular) that, either before or after birth, lead to complete destruction of the brain, with sparing of sub-tentorial structures.