In order to assess adequately the effectiveness of danazol, Gestrinone, and Buserelin, a prospective nonrandomized study was initiated in 126 patients with laparoscopically confirmed ovarian endometriosis. After hormonal therapy, laparotomy with microsurgical resection of endometriotic cysts was carried out. Regression (greater than 25%) of ovarian endometriosis was noted in 30%, 34%, and 73% of cases after danazol, Gestrinone, and Buserelin, respectively. The pregnancy rate in moderate endometriosis (53%) differed significantly from the rate obtained in severe endometriosis (45%). The highest percentages were found after Buserelin therapy. In conclusion, Buserelin emerged superior to danazol or Gestrinone treatment. Nevertheless, hormonal treatment leads to an incomplete suppression of ovarian endometriotic implants and this suggests the necessity of surgically removing invasive ovarian endometriosis.