OCCASIONALLY, reports of a rare malformation termed "sympodia" appear in the literature. The typical case report includes a description, usually fairly standard, of a macerated, stillborn, male fetus, immediately recognizable by fusion of the body from the waist down. It is this deformity which gave the condition the descriptive title of "siren" or "sirenomelus" which refers to the mythical mermaids of classical literature. Complete fusion, without vestiges of limbs is more specifically termed "sympus apus."1 The internal anatomy also usually shows the characteristic varying degrees of agenesis of the renal and genitourinary tracts, accompanied by malformations and segmental agenesis of the gastrointestinal tract. Malformations superior to the diaphragm2,3 are unusual. The present case is noteworthy for several reasons: (1) It occurred in identical twins. A search of the literature failed to disclose any previous reports of this malformation in identical twins. (2) Both infants were viable and in