Bcl-2 is a proto-oncogene initially described in follicular lymphoma, associated with chromosomal translocation(14;18). Recent studies have shown the presence of Bcl-2 in nonhematolymphoid tissue, especially in hormonally responsive tissue. The endometrium is an attractive model for studying the hormone dependent regulation of Bcl-2 expression. We have studied the immunoreactivity of Bcl-2 oncoprotein in relation to the immunoreactivity of estrogen receptors(ER) and progesterone receptors(PR) by immunohistochemistry in 52 human endometrial carcinomas, according to nuclear grade. The results obtained are summarized as followings, 1) Immunohistochemical grade of Bcl-2 showed a significant inverse correlation with nuclear grade. 2) Immunohistochemical grades of ER and PR also showed a significant inverse correlation with nuclear grade, and were well correlated with each other. 3) Immunohistochemical grades of Bcl-2 and hormone receptors showed a strongly significant correlation. On the basis of the above results, we suggest that Bcl-2 expression may be under hormone dependent control and that it can be used in prognosis and choice of hormonal therapy in the presence of hormone receptor.