The fetal hydantoin syndrome is a variable pattern of altered growth (pre and postnatal), mental deficiency, unusual facies, distal phalangeal hypoplasia, and other defects occurring in some infants exposed in utero to hydantoins. This altered pattern of morphogenesis is distinct from other recognized disorders. It has been reported only in the offspring of women using hydantoins. One case is presented and several aspects of the diagnosis are discussed.