The in vitro synthesis of secretory immunoglobulin A (SIgA) and carcinoembryonic antigen (CEA) was observed by tissue culture of biopsied gastric cancer tissue and gastric mucosa in other gastric diseases. The level of SIgA Synthesis in cultured gastric cancer tissue was lower than that in gastric mucosa in chronic atrophic gastritis, chronic superficial gastritis and normal stomach. The gastric mucosa of chronic gastritis can produce more SIgA than the normal gastric tissue, but the difference between chronic atrophic gastritis and chronic superficial gastritis was of no statistical significance. The CEA level was significantly higher in cancerous tissue than that in noncancerous ones, the amount of CEA synthesis by gastric mucosa in chronic atrophic gastritis was higher than that in chronic superficial gastritis and normal stomach. Well differentiated adenocarcinoma secreted much more SIgA and CEA than the poor-differentiated ones. The results suggest that the estimation of secretory function of SIgA and CEA be helpful for clinical diagnosis of gastric cancer.