Androgens produced by fetal Leydig cells (FLCs) during the masculinization programming window of fetal development play a critical role in the proper development of the male phenotype. An increased incidence of human male reproductive developmental disorders has occurred during recent decades (e.g. cryptorchidism, hypospadia, testicular cancer) and has been proposed to be due to environmental influences, including adverse actions of endocrine disruptors (EDCs) on FLCs steroidogenesis. This review covers the different classes of EDCs, such as pesticides that act as androgen receptor antagonists, phthalates and dioxins, which appear to inhibit fetal testosterone synthesis, as well as estrogenic compounds. The effects of these compounds on steroidogenesis by Leydig cells and the reproductive development are reviewed and their possible role in connection with the increasing frequencies of abnormalities in reproductive development is discussed.