A 23 year-old primigravida with bilateral congenital amastia was delivered at 38 weeks gestation following early rupture of the membranes. The mature newborn female also showed congenital bilateral amastia. In addition mother and daughter showed a mild hook finger of both 5th fingers. The mother only had 19 permanent teeth. About the permanent in the infant no data were obtained. This type of manifestation of a congenital anhydrotic ectodermal dysplasia is probably due to a sex-linked recessive gene. Newer investigations in experimental embryology show that the complete inhibition of the growth of the ectodermal milkridge occurs in the 6-12 th week of intra-uterine life and may also occur as an embryopathy due to dehydroepiandrosterone.