Objective: To evaluate the effect of the management modality of ovarian endometriomas on ovarian response to COH (controlled ovarian hyperstimulation) and ART (assisted reproductive technology) treatment outcome. Design: Retrospective case control study. Setting: Ege University Infertility-Family Planning Research and Treatment Center. Potients: 115 cycles of 84 patients who underwent ICSI-ET (intracytoplasmic sperm injection-embryo transfer) with ejaculated sperm were enrolled in the study. The endometrioma resection group (Group I) was comprised of 36 cycles in 29 patients who were treated with laparoscopic endometrioma cyst resection prior to treatment; endometrioma aspiration (Group II) was comprised of 26 cycles in 15 patients whose endometriomas were aspirated prior to treatment; and the control group (Group III) was comprised of 53 cycles in 40 patients for whom the only infertility cause was the tubal factor. Interventions: ICSI-ET treatment, laparascopic ovarian endometrioma cyst resection, transvaginal ultrasonography-guided endometrioma cyst aspiration. Main Outcome Measures: COH results and ICSI-ET treatment outcomes. Results: The groups were similar in all characteristics except for the mean age of the patients in group II being older than those in group I. Gonadotropin consumption was higher, peak estradiol level lower, and the number of oocytes less in the laparascopic resection group (Group I) with respect to the control group. The number of follicles was lower in the cyst aspiration group (Group II) with respect to the control group. The number of follicles larger than 15 mm, number of metaphase II oocytes, the fertilization, pregnancy and implantation rates were similar in all three groups. Conclusion: Interventions (laparascopic endometrioma resection, transvaginal ultrasound-guided endometrioma cyst aspiration) performed on endometriomas prior to ART treatment do not worsen the treatment outcome.