Abstract: Objective : To detect the expression of C-erbB-2 and COX-2 in hyperplastic and malignant endometrial ep-ithelial tissues and to explore the relationship between the expression levels of these two proteins. Methods : Immunohistochemistry (S-P method) was used to detect the expression of C-erbB-2 and COX-2 in 20 cases of normal proliferative endometrium, 23 cases of simple endometrial hyperplasia, 21 cases of complex en-dometrial hyperplasia, 43 cases of atypical endometrial hyperplasia, and 25 cases of endometrial adenocarci-noma. Results : The positive expression rates of C-erbB-2 and COX-2 were 4.5% and 9.1% in simple endome-trial hyperplasia, 4.8% and 14.3% in complex endometrial hyperplasia, 30.0% and 25.0% in low-grade atypi-cal endometrial hyperplasia, 60.9% and 52.4% in high-grade atypical endometrial hyperplasia, and 92.0% and 91.7% in endometrial adenocarcinoma, respectively.There was a significant difference in the expression of C-erbB-2 and COX-2 between hyperplastic and malignant endometrial epithelial tissue samples ( P =0.000).A positive correlation was found between C-erbB-2 and COX-2 expression ( P <0.01). Conclusion : An abnormal expression of C-erbB-2 and COX-2 may contribute to the pathogenesis and development of endometrial carci-noma.The combined detection of C-erbB-2 and COX-2 proteins may be valuable in distinguishing endometri-al adenocarcinoma from endometrial hyperplastic lesions.