In a comparison of follicular responses to controlled ovarian hyperstimulation (COH) between normal ovaries and ovaries previously treated by different laparoscopic techniques for ovarian endometrioma in 65 patients with unilateral endometrioma, laparoscopic ovarian fenestration and coagulation was performed in 24 cases (group 1) and laparoscopic ovarian cystectomy in the other 41 (group 2). In 16 patients with bilateral endometrioma (group 3), cystectomy was done in one ovary and fenestration and coagulation in the contralateral side. The results indicate that the response of ovaries to COH after laparoscopic ovarian cystectomy or fenestration and coagulation was the same and that there was no difference in response to COH between normal ovaries and those operated on by the laparoscopic techniques mentioned above.