A total of 129 infertile patients with endometriosis were treated by surgery. The severity of endometriosis was estimated according to Acosta's classification. The mean pregnancy rate was 51.2%. The pregnancy rate of the patients with primary infertility was 48.9% and, for the secondary infertility group, 56.8%. Two-thirds of the women who became pregnant conceived within one year. The pregnancy outcome in mild endometriosis was 59.1%, in moderate 56.4% and in severe 40%. Eighteen male partners had deficient sperm in the group of 63 women who did not conceive within the follow-up period. In addition to the extent of the disease, factors such as duration of infertility prior to surgery and age at the time of surgery seemed to be important in the fertility prognosis.