Objective：To study the different expression of heterogeneous nuclear ribonucleoprotein A2／B1（hnRNP A2／B1） among normal endometria, eutopic and ectopic endometria of patients with endometriosis. Methods：The expression differences among three normal proliferate-stage endometria， three proliferatestage eutopic and ectopic endometria of patients with endometriosis was examined by immunohistochemistry and Western blot. Results：hnRNP A2／B1 was located in the nucleus of both epithelial glands and stroma. The expression level of hnRNP A2／B1 in ectopic and eutopic endometria of patients with endometriosis both were weaker than that in normal endometria（P < 0.05）, while the difference between ectopic and eutopic endometria in the patients was not significant（P > 0.05）. Conclusion：hnRNP A2／B1 may play an important role in the pathogenesis of endometriosis.