We report the pedigree of a family in which a mother and her two children, a boy and a girl, all suffer from a similar, though variably expressed cerebral disorder, seen on CT as uni- or bilateral cavities within the supratentorial white matter in communication with the ventricular system. Additional white matter hypodensity around the lateral ventricles without ventricular widening provides preliminary evidence of a primary disease of myelination, in the absence of histopathological confirmation. This is probably the first report of "porencephaly" which shows a pattern of autosomal dominant inheritance.