To evaluate postoperative long-term cyclic and continuous administration of combined oral contraceptive (OC) pills in preventing endometriosis-related pain recurrence. Prospective, randomized, controlled trial. Tertiary care university hospital. Three hundred eleven women who underwent laparoscopic excision for symptomatic ovarian endometrioma. Patients were randomly divided into three groups: nonuser group receiving no therapy, and cyclic user group and continuous user group receiving low-dose, monophasic OC pills for 24 months in either cyclic or continuous administration. Presence and intensity of dysmenorrhea, dyspareunia, and chronic pelvic pain were assessed by a 10-point visual analogue scale (VAS) at 6, 12, 18, and 24 months postoperatively. A significant reduction in recurrence rate and VAS scores for dysmenorrhea was evident in the continuous users versus the other groups at 6 months, and in cyclic users versus nonusers at 18 months postoperatively. No significant differences in recurrence rate and VAS scores for dyspareunia and chronic pelvic pain were demonstrated among the groups. The increase of VAS scores from 6-24 months during the study period for dysmenorrhea, dyspareunia, and chronic pelvic pain was significantly higher in nonusers than in the other groups. Long-term postoperative use of OC pills can reduce the frequency and the severity of recurrent endometriosis-related dysmenorrhea.