Objective: To investigate effects of Aspirin on the growth of gastric cancer in vitro and in vivo. Methods: The effects of aspirin on the proliferation of SGC-7901 cells were measured by 3H-thymidine incorporation into DNA and cell cycle analysised by flow cytometric analysis, separately. COX-2 protein was examed in SGC-7901 cells by immunohistochemistry. The expression of c-Fos and AP-1 activity were detected by immunoblotting and EMSA separately. Results: Aspirin significantly decreased 3H-thymidine incorporation into SGC-7901 cells. Among concentration of 1