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Background: Although incidence and mortality have decreased, gastric cancer (GC) is still a public health issue globally. The international collaborative study for cancer survival using population-based cancer registry showed that the survival of GC was higher in Korea and Japan than other countries, including the United States of America (US). Aim: We examined the determinant factors of the high survival in Japan, compared with the US, with particular focus on the impact of the number of lymph nodes (LNs) examined for surgically treated patients. Methods: We obtained data on 88,447 cases from the nationwide GC registration project, the Japanese Gastric Cancer Association (JGCA), from 2004-2007. We also obtained 18,995 GC cases from US population-based cancer registry data from the Surveillance, Epidemiology, and End Results Program (SEER), diagnosed from 2004-2010. We estimated five-year relative survival and applied a multivariate excess hazard model to compare the two countries. We considered the effect of LNs examined on differences in survival. Results: Five-year relative survival in Japan was 79.8%, compared with 40.1% in the US. After controlling for confounding factors, we still observed significantly higher survival in Japan. The distribution of number of LNs examined showed notable differences between two countries. In over 50% of patients in the US, only 1 to 15 LNs were examined. A higher number of LNs examined showed better survival in both countries. The differences in excess death from cancer between countries were reduced in the category when more than 30 LNs were examined. Conclusion: Although it is difficult to remove biases to compare the two countries, stage migration, related to the more detailed retrieving strategy for LNs in Japan, is a key explanation for high survival in Japan. [ABSTRACT FROM AUTHOR]