Background: The effect of endometriomas itself on the ovarian responsiveness that relate to ovarian reserve had been reported with several inconsistent results. In one study evaluated women with unilateral endometriomas, ovaries with disease showed lower response to ovarian stimulation than contralateral healthy ovaries .However, recent study on infertile women with un-operated unilateral small endometriomas did not support difference in ovarian responsiveness. The aim was to evaluate the impact of presence of endometriomas on ovarian reserve as measured by circulating AMH. Methods: This retrospective study was carried out on 80 female patients in childbearing period attending outpatient clinic and/or inpatient department of obstetrics and gynecology at Tanat University Hospital and the study was conducted directly after approval in the period from Apri, 2019 till April 2020. Group (A): Study group: 60 female patients aged between 20 to 30 years old GROUP (B): Control group: 20 age matched female with healthy ovaries. Results: there is no statistical significant difference between groups as regard Menarche (years), Regularity and Amount of menstrual blood flow. There is statistical significant difference between groups as regard fixed tender Right Ventricular Failure. But there are no statistical significant differences between groups as regard nodule in rectovaginal septum, fixed tender adnexal masses, association with adenomyosis and infertility. There is highly statistical significant difference between case and control groups as regard AMH levels. there are highly statistical significant positive correlation between duration of endometriosis and each of presence of pelvic pain, cyst diameter and Visual Analogue Scale. Conclusions: Women with endometrioma have significantly lower serum AMH levels and seem to experience a more rapid decline in serum AMH levels than age matched counterparts, suggesting a harmful effect of endometrioma per se on ovarian reserve.