Although serum carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19–9 are commonly measured before surgery for gastric carcinoma, this clinical significance is not fully understood. We evaluated a total of 549 patients with gastric cancer who underwent gastrectomy. Levels of CEA and CA19-9 were measured preoperatively in all patients. We retrospectively analyzed correlations between CEA or CA19-9 and clinicopathologic features, and estimated the prognostic utility of the tumor markers by analyzing clinicopathologic characteristics of the carcinoma as a function of seropositivity or negativity of the antigens in combination or by raising the levels. The positivity rates of CEA (≥5 ng/mL) and CA19-9 (≥37 U/mL) were 19.5% and 18%, respectively. Serum CEA and CA19-9 positivity significantly correlated with depth of invasion, hepatic metastasis, and curativity. Forty-nine patients positive for both CEA and CA19-9 had significantly higher frequencies of lymph node metastasis, deeper invasion by the tumor, lower rates of curative resection (p< 0.01), and higher rates of hepatic metastasis (p< 0.05) than 377 patients with normal levels of CEA and CA19-9. Surgical outcomes of patients who were CEA-and CA19-9–positive were poorer than those of patients with normal CEA and CA19-9 levels (p< 0.01). Significant correlation was found between serum CEA and CA19-9 level (p< 0.001,r= 0.24). Doubling the threshold level of serum positivity to 10 ng/mL (CEA) and 74 U/mL (CA19-9) improved the prognostic value of these factors. However, multivariate analysis using Cox's hazards model revealed that only CEA positivity using the doubled threshold value (10 ng/mL) (p= 0.04, hazard ratio =1.7), nodal involvement (p= 0.01, hazard ratio = 1.9), and depth of invasion (p= 0.02 hazard ratio =1.5) significantly predicted prognosis. Carcinoembryonic antigen positivity using the doubled threshold level (10 ng/mL) was an important prognostic factor in patients with gastric cancer.