ObjectiveTo analyze the ovarian reserve via measurement of follicular density and anti-Müllerian hormone (AMH) in endometriosis patients participating to a clinical program of cortical ovarian cryopreservation.DesignRetrospective analysis of serum AMH levels and prospective investigation of ovarian follicle number.SettingUniversity Hospital.Patient(s)Two hundred and two women with endometriosis and 400 controls.Intervention(s)Blood samples and ovarian biopsies.Main outcome measure(s)Correlation of serum AMH levels and the number of non-growing follicles in the biopsied cortical tissues in endometriosis and control subjects, including age, type of AMH kit, and the laboratory performing the analysis as covariates.Result(s)AMH levels were shown to decrease with age in untreated endometriosis patients (P