Anti-Müllerian hormone (AMH) is a glycoprotein belonging to the transforming growth factors (TGF-P). AMH plays a fundamental role in the regression of Müllerian ducts in male embryo. In its absence, Müllerian ducts develop into female inner reproductive organs. In boys, it is significantly produced in Sertoli cells of testes until puberty and then slowly decreases to residual values for the rest of the men's life. AMH serves as a biochemical marker of the presence of testes in cryptorchidic males. In females, AMH is secreted by granulosa cells of small follicles in the ovary. Serum values are almost undetectable during infancy and then rapidly increase with the onset of puberty, reflecting the initial recruitment of primordial follicles. AMH is produced in growing follicles until they reach a stage when dominant follicle is detached from a cohort of antral follicles. The measurement of serum AMH levels during woman's reproductive life represents an ideal tool for the assessment of the ovarian follicular reserve. The advantage of AMH in relation to the ovarian steroid hormones is that serum levels do not fluctuate significantly during the menstrual cycle. In addition, circulating AMH strongly correlates with antral follicle count (AFC), visualized by ultrasound in the follicular phase of the cycle. As the number and quality of the oocytes diminish throughout the woman's reproductive life, serum concentrations of AMH gradually decrease and fall below detectable levels in menopause. This could be of particular interest in subfertile and infertile women undergoing assisted reproductive techniques (ART) in achieving pregnancy.