['Cyclooxygenase-2 (COX-2) expression appears to be increased in several different types of human cancers, suggesting that the presence of COX-2 is associated with carcinogenesis. Recently, increased expression of COX-2 has been frequently detected in gastric cancer, and this may have prognostic significance. In the present study, we aimed to analyze the expression of COX-2 in a much larger sample to determine whether COX-2 expression is related to the clinicopathological features and survival rates of patients with gastric cancer.', 'We investigated 140 patients with gastric cancer who underwent surgery between January 1992 and December 1993 and examined the expression of COX-2 in human gastric cancer tissue by immunohistochemistry.', 'COX-2 expression was present in the cytoplasm of tumor cells but not in normal gastric epithelia. Positive expression of COX-2 was detected in 86 of 140 gastric cancers analyzed (61.4%). Positive expression of COX-2 correlated with the depth of tumor invasion (p = 0.015). However, there was no association between COX-2 expression and tumor stage or status of lymph node or distant metastasis. Furthermore, COX-2 expression was not associated with patient survival (p = 0.816). Positive expression of COX-2 occurred more frequently in intestinal than in diffuse or mixed types of cancer and correlated with tumor differentiation (p < 0.001, p = 0.001, respectively).'] Is cyclooxygenase-2 expression associated with well-differentiated and intestinal-type pathways in gastric carcinogenesis?