Serum tumor markers CEA, CA19-9, CA72-4 and Helicobacter pylori (H.pylori) antibodies were measured in 162 patients with gastric cancer. CEA, CA19-9 and CA72-4 had sensitivities of 24.0%, 35.5% and 21.9% respectively. CA72-4 provided 100% specifity, compared to 77% and 93% for CA19-9 and CEA. The positive predictive value (PV) in CEA, CA19-9 and CA72-4 was higher than negative PV. Serum CA19-9 and CA72-4 levels rose in tumor of ＞5.0cm in diameter. The CA19-9 increased remarkably when the deeper stomach wall was invased. The significantly elevated CEA, CA72-4 and CA19-9 levels were found in patients who had nodal involvement in more than 50% and distant metastasis. However, the increase of CEA, CA19-9 and CA72-4 were found in undifferentiated tumor. Antibodies to H.pylori were detected in 54% of patients but in only 22% control subjects. A significant association was found between H.pylori infection and gastric cancer (odds ratio=3.75; 95% confidence interval=2.11-5.41, Ｐ＜0.01). Conclusions: CEA, CA19-9 and CA72-4 have higher specifity but lower sensitivity in diagnosis of the gastric cancer. The levels of CEA, CA19-9 and CA72-4 are significantly associated with the diameter, the depth of invasion, nodal involvement, distant metastasis and cell differention. Infection with H.pylori may be an important cause of gastric cancer.