Objective : Gastric carcinoma is one of the most common cause of death in Korea with limited effectiveness of chemotherapy. Thymidylate synthase(TS) is a critical therapeutic target for the fluoropyrimidine cytotoxic drugs, that are the mainstay of the treatment for the advanced gastrointestinal malignancies. We assessed the relationship between the levels of TS expression and survival and effect of 5-fluorouracil based chemotherapy in gastric adenocarcinoma. Methods : Thirty six patients with gastric adenocarcinoma who underwent curative resection of stomach at Ewha Womans University Hospital were evaluated. TS protein expression in tumor tissues was assessed by standard immunohistochemical staining techniques with TS 106 monoclonal antibody. Results : TS expression was high(3+) in 19 patients (52.8%) and low(≤2+) in 17 patients(47.2%). Between these two groups, there was no significant difference in the histopathologic type or stage. Seventy-two point five percent of patients with low TS expression were disease free at 5 years compared with 58.2% of patients with high TS expression(p=0.31) and 73.7% of patients with low TS expression were alive at 5 years compared with 61.4% of patients with high TS expression(p=0.34). In patients with high TS expression, disease-free survival (DFS) and overall survival(OS) of patients who received adjuvant chemotherapy were longer than those of patients with surgery alone without significance(p=0.28, p=0.16). Conclusions : We could not confirm the association between the level of TS expression in tumor tissues and DFS and OS of patients with gastric adenocarcinoma who underwent curative resection. Further study with more cases as well as prospective study will be necessary for establishment of relationship between TS expression of tumor and prognosis of gastric adenocarcinoma