OBJECTIVE Cancer for a long time has been recognized as a fatal disease. Thus it is known to be major health problem in many countries throughout the world. In recent years, cancer morbidity and mortality increased in our country and especially gastric cancer has second order among all cancers. The aim of this study was to analysis the survival of patients diagnosed with gastric cancer and the factors which modify prognosis. METHODS Retrospective study of overall patients diagnosed with gastric cancer registered in the cancer registry center of Research Center for Gastroenterology and Liver Disease (RCGLD), Shahid Beheshti University, M.C, Tehran, Iran, between Dec. 2001 and Dec. 2006 was done. Survival status of patients was followed by the telephone contact. The Kaplan-Meier statistical method was employed to determine the probability of survival and log-rank test to compare those. Cox regression was used to determine prognosis factors. P < 0.05 was considered as statistically significant. All calculations were carried out by SPSS (version13.0) statistical software. RESULTS Of 746 patients, 38.6% are dead. The mean and median survival time was 42.45 and 22.8 months, respectively and five-year survival rate was 25.3%. With univariate analysis, Age at Diagnosis, surgery treatment, type of first treatment, pathologic stage, tumor size, histology type of tumor, extent of wall penetration and pathologic distant metastasis were significant prognostic factors related to overall survival time. Tumor size greater than 35mm (HR = 2.12) and have a metastasis (HR = 2.04) were found to be the statistically significant poor prognostic factors related to survival in multivariate analysis. CONCLUSIONS According to results, early detection of cancer in lower ages and in primary grades of tumor is important to increase patient's life expectancy.