To study ovarian follicular dynamics during chemotherapy to understand the mechanisms behind chemotherapy-induced ovarian follicular depletion and to evaluate whether pretreatment levels of ovarian reserve markers were predictive of the posttreatment levels.Prospective clinical study.University hospital fertility center.Seventeen women (median age 30 years; range 19–35 years) undergoing chemotherapy.Patients were seen before, frequently during, and after chemotherapy, until 1 year after the end of treatment. Antral follicle count and levels of FSH, LH, E 2 , anti-Müllerian hormone (AMH), and inhibin A and B were monitored at each visit.The dynamics of the ovarian reserve markers during chemotherapy and factors predictive of posttreatment ovarian function.Anti-Müllerian hormone level (mean ± 2 SEM) dropped from 2.7 ± 1.0 to 1.1 ± 0.6 and to 0.4 ± 0.4 ng/mL immediately after one and two series of chemotherapy, respectively. Inhibin B and antral follicle count decreased after three series whereas FSH reached menopausal levels after four series. High pretreatment AMH levels predicted higher posttreatment AMH levels.Anti-Müllerian hormone and inhibin B levels immediately declined in response to chemotherapy, and the follicular target of chemotherapy appeared to be growing follicles. High pretreatment AMH levels were predictive of a higher posttreatment AMH level.