Purpose: Gastric cancer is prevalent in Korea, therefore the purpose of this study was to determine the clinicopathologic characteristics, 5-year survival rate, and prognostic factors for gastric patients who underwent gastrectomy by a single surgeon. Materials and Methods: A total of 1,435 patients diagnosed with gastric cancer who underwent gastrectomy in the Department of Korean Gastric Cancer Center at Seoul Paik Hospital between September 1998 and August 2003, and the gender, age, location and size of the tumor, visual and histologic analysis, depth of invasion, lymph node metastasis, invasion (perineural, venous, and lymphatic), and surgical method were examined retrospectively. Results: The ratio between males and females was 2.29 : 1, and the average age was 56.7 years. Based on the UICC TNM classification, the patients were distributed as follows: IA 35.4%, IB 14.1%, II 12.6%, IIIA 12.3%, IIIB 8.3% and IV 17.3%. The 5-year survival rate was 69.6%. The results of univariate analysis showed that there were significant differences in the survival rate by age, location and size of tumor, Borrmann type, level of differentiation, Lauren's classification, depth of invasion, metastasis in lymph nodes, UICC TNM stage, invasion (perineural, venous, and lymphatic), and surgical method. Based on multivariate analysis, only the depth of invasion and lymph node metastasis were independent prognostic factors. Conclusion: Although various clinicopathologic characteristics affect the prognostic factors of the patients with gastric cancer, the results of this study showed that the stage of disease, such as depth of invasion and metastasis in lymph nodes, are the most critical factors. There is a need to establish the diagnosis of gastric cancer early and to study and develop various treatment methods based on the diagnostic factors in order to improve the survival of patients with gastric cancer.