An anencephalic infant with holoprosencephalic facies and ring chromosome 18 [r(18)] is reported with review of the pertinent literature. Although the association of anencephaly and holoprosencephalic facies is well established, this is the first instance of an accompanying karyotypic abnormality. Review of other r(18) cases suggests that this is not a coincidental finding. Karyotype analysis appears warranted in cases of anencephaly with holoprosencephalic facies.