BACKGROUND: Lymph node metastasis in patients with gastric cancer is one of the important prognostic factors. However, there is no consensus concerning the best classification for lymph node metastasis as a prognostic factor. So, to evaluate the ratio of the number of metastatic lymph nodes to the total number of dissected lymph nodes (the ratio of LN meta) as a prognostic factor, we compared the ratio of LN meta with lymph node status according to the Japan Classification of Gastric Carcinoma and the total number of metastatic lymph nodes with multivariate analysis.METHODS: Between 1991 and 1997, a total of 360 patients with primary gastric cancer who underwent gastrectomy with D2 or more extended lymph node dissection were included in this study. Ten kinds of prognostic factors and three types of different classifications for lymph node metastasis were analyzed by multivariate analysis using the Cox regression.RESULTS: The average number of dissected lymph nodes and metastatic lymph nodes were 55.0 (range, 11-184) and 2.6 (range, 0-86), respectively. There were significant differences of the 5-year cumulative survival rates among each group of the ratio of LN meta (0%, 1%-9%, 10%-24%, and more than 25%). Age, tumor size, curability, and the ratio of LN meta were selected as independent prognostic factors by forward stepwise selection. The ratio of LN meta showed the highest hazard ratio by Cox regression.CONCLUSION: The ratio of LN meta appears to be an important prognostic factor and the best classification factor for lymph node metastasis.