Although hydrocephalus is usually a sporadic disorder which rarely recurs in the same family, there is a rare, but clearly delineated, syndrome in which recurrence is to be expected. This syndrome of sex-linked hydrocephalus is caused by congenital aqueductal stenosis. It is probably due to a defective recessive gene on an X chromosome. Female carriers are unaffected, but certain of their male offspring are apt to be affected. In genetic counseling of parents who have had one hydrocephalic infant, especially a male, one should be aware that this syndrome exists. A case of this syndrome is presented with autopsy findings, and pedigree.