Anti-Müllerian hormone (AMH) is synthesized by immature Sertoli cells and by postnatal granulosa cells. Assay of serum AMH is useful in clinical situations to search for the presence of testicular tissue or to assess its functional value before puberty. At the time of puberty, serum levels of AMH decrease dramatically, a negative correlation has been demonstrated between AMH and testosterone serum levels. AMH assay is also useful in a rare form of male pseudohermaphroditism, characterized by the persistence of uterus and tubes in an otherwise normally virilized patient. AMH levels are undetectable or severely decreased in the case of a mutation of the AMH gene itself. In contrast, the concentration of serum AMH is normal if the syndrome is due to an insensitivity of AMH target organs.