Sixty patients with endometriosis, stage I-IV, diagnosed by laparoscopy or laparotomy, were treated with 200 micrograms of domestic luteinizing hormone-releasing hormone analogue (LHRH-A) subcutaneously twice daily, starting from the early follicular phase for 6-10 months. Serum FSH and LH levels elevated at first declined significantly thereafter, and remained low after the sixth day of treatment. Serum E2 concentrations were suppressed below that of the early follicular phase or to the castrated levels after one month of therapy. Symptoms and signs of endometriosis improved markedly during the treatment and patients became anovulatory and amenorrheic. At the end of treatment, resolution of endometriotic implants and softening of adhesions were shown under the second laparoscopy. Endometrial biopsies revealed inactive endometrium. After discontinuation of the treatment, ovulatory menses returned within 34-72 days, more than half of the patients complicated with infertility for 2-10 years became pregnant within 1-8 months. The recurrence rate was 37% after 0.5-5 year follow-up. Side effects were only related to hypooestrogenism. These data indicated that LHRH-A therapy had the effect of temporary reversible medical oophorectomy, and was therefore an effective approach for the treatment of endometriosis.