Ectodermal dysplasias (ED) are a heterogeneous group of disorders characterized by developmental dystrophies of ectodermal structures, such as hypohidrosis, hypotrichosis, onychodysplasia and hypodontia or anodontia. All forms of this heterogeneous group are genetically transmitted. Two genes are localized and identified, namely ectodermal dysplasia anhidrotic (EDA) and downless (DL). Currently the genes and gene products are defined, but the function of the proteins is not fully known. The location of the genes has enabled prenatal diagnosis and a more accurate identification of possible carriers. Medical counseling provides genetic information concerning the specific diagnosis, recurring risks, prenatal approach, identification of risk carrying relatives, and social, economic and psychological problems. Evaluation and diagnosis are essential immediately after birth.