The symptomatology in 24 patients with the embryo-fetal alcohol syndrome in this study corresponded essentially to the clinical picture described by Lemoine et al., and Jones et al., although we were not able to confirm the maxillary hypoplasia and microphthalmia mentioned in the latter. In addition, we observed in 2 girls a virilization of the genitalia which corresponded to female pseudohermaphroditism. Auxologically a nearly regular pattern of the parameters measured was found. The intra-uterine hypotrophy continues after birth. In particular, the head circumference, reflecting the brain growth, remains low. The cerebral damage leads to oligophrenia with a typical pattern of psychic and motor behaviour. Moderate cases tend to improve. Concerning the pathogenesis, the clinical observations in connexion with recent animal experiments permit the following conclusions. Neither the malnutrition nor the liver damage of the mothers are necessary presuppositions. Ethanol itself appears to play the main teratogenetical rôle. Acetaldehyde, which is the primary metabolite of ethanol, is cytotoxic too. However, the liver of the embryo and the fetus, in consequence of its deficient alcohol dehydrogenase content, is not able to metabolize ethanol.