Abstract: Objective :To study the expression of cyclooxygenase-2 (COX-2) protein in different subtypes of intestinal metaplasia (IM) of the gastric mucous membrane and gastric carcinoma, explore the possibility of forecasting the risk of malignant potential of IM with COX-2, and to investigate therelationship between COX-2 expression and gastric carcinogenesis. Methods :A total of 40 cases of chronic atrophic gastritis (CAG) with IM, 40 cases of gastric carcinoma, and corresponding paracancer-ous tissues were selected, respectively, in order to construct a tissue microarray. High iron diamine /alcian blue (HID/AB) staining and Hematoxylin and Eosin (HE) staining was used to classify IM and gas-tric carcinoma, and the expression of COX-2 protein was assessed using immunohistochemistry. Results :The positive rate of COX-2 expression was 60.87%, 75.00%, and 86.36% in IM foci in CAG, IMfoci in paracancerous tissues, and the intestinal-type gastric carcinoma, respectively, and there was no significant difference among them. However, the expressional intensity of COX-2 protein showed agradually increased tendency in the sequence of IM foci in CAC;IM foci in paracancerous tissues-intestinal- type gastric carcinoma (P<0.005). The positive rate and intensity of the expression of COX-2protein in the intestinal- type gastric carcinoma wire all significant higher compared to the diffuse-type gastric cancer (P<0.005). The expressional positive prevalence of COX-2 protein in type III IM was significant higher than that in type I and type II (P<0.05), and the expressional intensity also showed a gradually increased tendency from type I to type III (P<0.005). Conclusions : The expressional level of COX-2 increases gradually with the increase of the risk of malignancy of I and its expressional level may be a useful index to forecast the risk of malignant potential of IM. COX-2 expression is associated with the intestinal- type gastric carcinoma, but it might also have some role in the carcinogenesis of the diffuse- type.