Objective: As endometrioma frequently recurs after conservative surgery, long-term postoperative medical treatment for the prevention of recurrence is necessary. However, it has not been elucidated whether long-term postoperative medical treatment is crucial to all patients until menopause. Thereupon, this study was conducted to evaluate the age-related recurrence patterns after conservative surgery for endometrioma. Study design: A retrospective cohort study was performed on a total of 420 reproductive-aged women who underwent conservative surgery for endometrioma between January 2000 and December 2010. Ultrasonography was used during the follow-up period to detect endometrioma recurrence. Patients were classified into two groups according to the use of postoperative medications. The first group was observation only, while the second received gonadotropin releasing hormone agonists followed by cyclic oral contraceptives. The cumulative recurrence rate of endometrioma was compared according to the age at surgery (20-29 years, 30-39 years, 40-45 years) within each group. Subgroup analysis was performed according to the age between the two groups. Results: The median follow-up duration after surgery was 29.0 months (range 6-159 months) for all patients. After adjusting for parity, size and bilaterality of cyst, and stage with American Society for Reproductive Medicine classification of endometriosis which was statistically different, within the group of no treatment, the cumulative recurrence rate in 40-45 years (10.2%) was significantly lower compared with those in 20-29 years (43.3%; hazard ratio (HR) = 0.04; 95% confidence interval (CI) = 0.01-0.52) and 30-39 years (22.5%; HR = 0.19; 95% CI = 0.04-0.92). However, there were no differences within the group of postoperative medical treatment. When we compared between the two groups, the cumulative recurrence rate was significantly different in 20-29 years (8.1 vs 43.3%; p < 0.001) and 30-39 years (5.4 vs 22.5%; p = 0.007), but there was no difference in 40-45 years (4.5 vs 10.2%; p = 0.901). Conclusions: Our preliminary results demonstrate that the risk of endometrioma recurrence decreases with age. After the age of forty, the recurrence rate does not differ according to the use of postoperative medication. Based on our results, postoperative medical treatment may be individualized according to the patient's age at the time of surgery. Further studies are needed to identify patients who may benefit from postoperative medication. (C) 2016 Elsevier Ireland Ltd. All rights reserved.