In recent years, assisted reproductive technology (ART) has undergone marked development and has come to play a central role in reproductive medicine. Although controlled ovarian stimulation (COS) has also improved, assessment of the ovarian reserve has become important for further improving stimulation. Existing methods of ovarian reserve assessment are inadequate, and antiMüllerian hormone (AMH) has recently garnered attention as a marker for ovarian reserve. AMH is not influenced by the menstrual cycle, can be measured at any time by collecting blood, and correlates very strongly with the number of eggs collected during in vitro fertilization. Whereas basal FSH (a conventional marker) changes after actual decreases in ovarian reserve, AMH enables quantitative prediction of ovarian reserve and is important for determining strategies for fertility treatment. Many infertile patients have AMH levels close to zero and are potential cases of premature ovarian failure. As the number of elderly infertile patients is increasing rapidly and fertility treatment is shifting from the reproductive stage to the non-reproductive stage, markers that are unstable during menopause, such as basal FSH and E2, are becoming unreliable. AMH is expected to play an increasingly important role and may become a routine test in fertility treatment.