Objectives: We have reported that apoptotic bodies can estimate the ovarian function in the patients involved into IVF treatment and that the patients who have many oocytes harvested showed the lower rate of apoptotic bodies and the patients with a few oocyte showed the higher rate of apoptotic bodies. Endometriosis patients revealed higher rate of apoptotic bodies than the other infertility causes. Moreover the patients with pregnancy by IVF showed lower rate of apoptotic bodies than the patients without pregnancy. In this study we examined the relationship between the grade of endometriosis and the rate of apoptotic bodies.Designs: Apoptotic bodies of granulosa cells in endometriosis patients were measured and the effects of endometriosis on the ovarian function were examined.Materials and Methods: Prior to IVF-ET treatment, patients (n = 40) with endometriosis were assessed by laparoscopic examination according to R-AFS classification. Patients were stimulated by Gn-RH agonist (Buserelin), hMG/FSH and hCG. Gn-RH agonist started to be used from mid luteal phase of the previous cycle until the day of hCG administration. HMG started on day 3 of the cycle. When the mean diameter of a leading follicle was more than 16, hMG injection was stopped and hCG was administrated. Thirty-five hours after hCG injection, follicles were aspirated under ultrasound guide. Both cumulus granulosa cells and mural granulosa cells were dispersed by hyaluronidase, fixed by formalin on each slideglass. The slideglasses were stained by Hoechist 33258 and one thousand granulosa cells were observed and apoptotic bodies were counted by a fluorescence microscope.Result: In proportion to the grade of R-AFS classification (I to IV), the rate of apoptotic bodies increased both in cumulus cells and in mural cells (mural: 0.55 + 0.09, 0.96 + 0.22, 1.89 + 0.39, 1.6 + 0.24; cumulus: 0.15 + 0.07, 0.33 + 0.07, 0.64 + 0.08, 0.64 + 0.12) (mean + SEM). And in the IVF treatment cycles, the patient with chocolate cysts showed higher rate of apoptotic bodies than the patients without a chocolate cyst (chocolate+: mural :2.14 + 0.18, cumulus:0.93 + 0.1, chocolate-: mural: 1.23 + 0.2, cumulus: 0.4 + 0.05).Conclusions: From the point of apoptotic bodies, in proportion to the R-AFS grade of endometriosis the follicle development was disturbed. Moreover in the IVF treatment cycles, the patients who had the obvious endometriosis lesion in ovaries showed higher ovarian dysfunction than the patients without a ovarian endometriosis lesion.