No congenital malformation in infants is more profound than anterior craniofacial duplication. The precise term for this rare anomaly is diprosopus, referring to a fetus with a single trunk, normal limbs, and varying degrees of facial duplication. A search of the world literature produced only 16 cases of diprosopus since 1864. Despite the rarity of this anomaly, three such infants were born in the Southern California area during the past year, making this the largest reported series to date. The three infants were born with two distinctly formed faces. Each had four separate eyes, two mouths, two noses, and two ears with a primitive ear or sinus tract at the plane of fusion. In addition, multiple congenital aberrations existed which involved a variety of internal organs. The pathogenesis of diprosopus is not well understood, but environmental stress early in embryologic development has been suggested as a possible factor. The apparent mechanism is a slowing of pregastrulation oxidation with resultant focal developmental arrests.