Prenatal diethylstilbestrol (DES)-exposed mice have raised the suspicion of a transgenerational effect in theoccurrence of genital malformation in males. This nationwide cohort study in collaboration with a Frenchassociation of DES-exposed women studied 529 families and showed that a significant proportion of boys born toDES daughters exhibited hypospadias with no other molecular defects identified. (Fertil SterilÒ 2011;-:-–-.Ó2011 by American Society for Reproductive Medicine.)Key Words: Hypospadias, DES, diethylstilbestrol, estrogens, prevalence, environment, epigenetic