OBJECTIVE: This study examines the influence of ovarian endometrioma on fertility. STUDY DESIGN: For 117 infertile Women who were diagnosed as having endometriosis by laparoscopy and who underwent danazol therapy, we examined (1) the relationship between ovarian endometrioma and level of bead-phagocytotic macrophages in ascites and the interleukin-1 beta level, (2) the relationship between ovarian endometrioma and pregnancy rate during the 36 months after danazol therapy, and (3) the relationship between ovarian endometrioma and pregnancy rate, considering the severity of the lesion on the bilateral tubes and the pelvic peritoneum. RESULTS: (1) The levels of bead-phagocytotic macrophages in patients with or without ovarian endometrioma were 68% and 67%, respectively (not significant). Similarly, no significant difference was seen in the interleukin-1 beta positive rate between the two groups. (2) The pregnancy rates of the former group and the latter group were 36% and 43%, respectively (not significant). (3) The existence or absence of ovarian endometrioma made no significant difference in the pregnancy rate in a group of patients with no lesions in the bilateral tubes or in another group with no lesions and scattered endometriotic implants on the peritoneum. CONCLUSION: It seems unlikely that ovarian endometrioma itself significantly impedes fertility after danazol therapy.