Two siblings, one a male pseudohermaphrodite and the other female, died on the first day of life. In both instances pregnancy was complicated by polyhydramnios. At autopsy each was found to have multiple abnormalities, some concordant, others discordant. The concordant ones were hypoplastic left-heart complex, absent pulmonary lobation, polydactyly, bilateral talipes, and, on microscopic examination, some large atypical cells in the pancreatic islets. Chromosome cultures failed to grow. As far as is known parents were unrelated. Autosomal recessive inheritance is considered a possible cause, and the infants are thought to have the most severe form of the so-called Smith-Lemli-Opitz (RSH) Syndrome.