Thirty-two patients with laparoscopic diagnosis of endometriosis were treated for 6 months with the gonadotropin-releasing hormone agonist goserelin depot. Hormonal and clinical evaluations were conducted during treatment and for a 6-month follow-up period. Serum 17 beta-estradiol levels were sharply suppressed. Luteinizing hormone was also decreased, whereas follicle-stimulating hormone, after an initial fall, gradually rose to pretreatment levels. Ovarian androgenic production was less inhibited, total testosterone being the only significantly suppressed hormone. There was a marked improvement of signs and symptoms of endometriosis and a 47.3% reduction of laparoscopic score. The results of this study suggest that goserelin depot provides a very good suppression of ovarian estrogen production and is highly effective in decreasing the symptoms of endometriosis with an acceptable compliance by the patient.