In order to adequately assess the effectiveness of danazol, gestrinone, buserelin-nasal spray (IN) and buserelin-implant (SC), a prospective non randomized study was initiated in 178 patients with laparoscopically confirmed ovarian endometriosis. After hormonal therapy, laparotomy with microsurgical resection of endometriotic cysts or laparoscopy laser was carried out. Regression (greater than 25%) of ovarian endometriosis was noted in 30, 34, 73 and 91% of cases after danazol, gestrinone and buserelin IN and buserelin SC respectively. Histological study proves that hormonal treatment leads to an incomplete suppression of ovarian endometriotic implants and this suggests the necessity to remove surgically invasive ovarian endometriosis. The pregnancy rate in moderate endometriosis (55%) differed significantly from the rate obtained in severe endometriosis (44%). The highest percentages were found after buserelin therapy. In conclusion, preoperative use of a potent GnRH agonist, administered subcutaneously, seems to be the best therapeutic approach when associated to surgery (CO2 laser or microsurgery)