ObjectiveTo study the expression of cyclooxygenase2 (COX2) and its clinical significance in gastric carcinoma. MethodsThe expression of COX2 in 47 cases of gastric carcinoma and 16 cases of normal gastric tissue were detected by SP immunohistochemical technique. Helicobacter pylori (H.pylori) infection was diagnosed by urease experiment and Giemsa staining.ResultsThere was no positive signal of COX2 detected in normal gastric tissue. The positive expression rate of COX2 was 63.8%(30/47) in gastric carcinoma.The expression of COX2 was correlated with TNM stage, lymph node metastasis and H.pylori infection(P<0.01). Positive COX2 expression rate in H.pylori infection group was 72.4%(21/29), significantly higher than that in the group without H.pylori infection.Conclusion COX2 expression is involved in the carcinogenesis and malignant progression of gastric carcinoma.The examination of COX2 may be helpful to judge biological behavior of gastric carcinoma.