BACKGROUND/AIMS: Lymph node metastasis (pN) is one of the most significant prognostic factors in patients with gastric cancer. The pN classification of the Japanese Gastric Cancer Association (JGCA) is based on the anatomical site of metastatic nodes from the primary tumor, whereas that of the International Union Against Cancer (UICC) is based on the number of nodes involved. The purpose of this study was to determine which system is more useful for predicting patient outcomes. METHODOLOGY: From 1992 to 2002, a total of 318 patients at our hospital underwent surgical resection with lymph node dissection for primary gastric cancer. Their medical records were examined, and the overall survival rates were compared between the two pN classification systems. RESULTS: Under the JGCA system, there was a significant difference in patient survival between pN0 and pN1 and between pN1 and pN2 but not between pN2 and pN3. Under the UICC-TNM system, there was a significant difference in patient survival between all pN classes. When the JGCA-pN1 and JGCA-pN2 classes were regrouped as UICC-pN1 and UICC-pN2-3, respectively, the survival rate was still better for the UICC-pN1 class than for the UICC-pN2-3 class. CONCLUSIONS: The better differentiation of outcomes by the UICC-pN system suggests that the number of metastatic lymph nodes is more important than the anatomical site in predicting outcomes.