Contrary to what is observed in true hermaphroditism and in male pseudo-hermaphroditism, there is no erroneous transmission of the genetic gonadal differentiation programme in female pseudohermaphroditism. All that has happened is virilization of the urogenital sinus and external genitalia in a foetus exposed to exo- or endogenous androgens. In the absence of testis there is no production of anti-mullerian hormone, and for these reasons the uterus, the fallopian tubes and the vagina develop normally, whilst the wollfian ducts are regressed and there is no trace of male deep spermatic pathway. On the basis of recent acquisitions in biochemistry, endocrinology and embryogenesis, the authors compare the various degrees of virilization with the biochemical abnormalities.