Anti-mullerian hormone (AMH), also known as Mullerian inhibiting substance, is a key factor in embryonic sex differentiation in males. In postnatal females, AMH is secreted by the primary, secondary and antral follicles and appears to regulate early follicular development. Beside AMH inhibits mullerian duct development in the male fetus, it seems to have other functions in the ovary and may play a role in ovarian cancer. Several studies suggest that the measurement of mullerian inhibiting substance in serum may be used to early detect persistent or recurrent disease in patients with ovarian sex-cord tumors. In addition, immunoreaction of AMH expression in tumor cells helps to distinguish between granulosa or Sertoli cell tumors and other gonadal tumors of different origins.