en Gynecology & Obstetrics Gynecology & Obstetrics Original Research Original Research <p> <strong> Background </strong>: To determine the role of Letrozole, an aromatase inhibitor,in the treatment of endometriotic pain.<strong></strong> </p><p> <strong> Methods: </strong>In this prospective, randomized, controlled clinical trial in minimallyinvasive surgery research center,51 women with pelvic endometriosis and endometriotic pain (dyspareunia, dysmenorrhea, pelvic pain) score of 5 or more (for at least one of these endometriotic pain), after laparoscopic diagnosis and conservative laparoscopic surgery were treated with either Letrozole plus OCP (n=25) or only OCP (n=26) for 4 months continuously. </p><p> <strong> Results: </strong>Using VAS test, the score of dyspareunia, dysmenorrhea and pelvic pain 4 months after the laparoscopic surgery declined significantly in both groups but the difference between results of the two groups was not significant. </p><p> <strong> Conclusion: </strong>Both treatment modalities showed comparable effectiveness in the treatment of pains related to endometriosis and in comparison with OCP, Letrozole did not affect the outcome.<strong></strong> </p><p>  </p> Aromatase inhibitor, Endometriosis,Letrozole, Pelvic pain. 695 701 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1501-3&slc_lang=en&sid=1 Fariba Almassinokiani dralmassi@yahoo.com 200319475328460013550 200319475328460013550 No Minimally Invasive Surgery Research Center, Iran University of Medical Sciences, Department of gynecology and obstetrics, RasoolAkram Hospital, Tehran, Iran. Alireza Almasi a_almasi_n@hotmail.com 200319475328460013551 200319475328460013551 Yes Iran University of Medical Sciences, Firoozgar Hospital, Tehran, Iran. Peyman Akbari thekingofkings_angle@yahoo.com 200319475328460013552 200319475328460013552 No Tehran University of Medical Sciences, Department of gynecology and obstetrics, RasoolAkram Hospital, Tehran, Iran. Mahboubeh Saberifard msaberi@hyhoo.com 200319475328460013553 200319475328460013553 No Iran University of Medical Sciences, Department of Gynecology and Obstetrics, RasoolAkram Hospital, Tehran, Iran.