Focal dermal hypoplasia is characterized by widespread dysplasia of mesodermal and ectodermal structures, including undevelopment and maldevelopment of the dermis. Approximately 46 such cases are now known and we are reporting two additional children. The abnormal findings in previously published cases have been collected and are presented in tabular form. This syndrome must be distinguished from congenital poikiloderma, connective tissue nevi, anhidrotic and hidrotic ectodermal dysplasias, and incontinentia pigmenti. Some cases of localized congenital absence of the skin may represent incomplete forms. Presently available evidence suggests that the focal dermal hypoplasia syndrome is genetically determined.