This study attempted to clarify the prognostic factors in advanced gastric cancer, with special reference to lymph node metastasis. It was a retrospective study of 401 patients with stage III and IV gastric cancer operated on during the 5 years from 1988 to 1993. A significant relationship was found between the 5-year survival rate and (1) the ratio of the number of metastatic lymph nodes to the total number of dissected lymph nodes (ratios of 1-15, 16-30 and 31 per cent or more were associated with a 5-year survival rate of 81, 23 and 17 per cent respectively), (2) stage N1 or N2 of the Union International Contra la Cancrum tumour node metastasis classification (58 and 27 per cent respectively) and (3) the number of metastatic lymph nodes (1-3, 4-7 and 8 or more were associated with a 5-year survival rate of 67, 49 and 32 per cent respectively). Multivariate survival analysis using Cox's proportional hazard model was applied to these three forms of lymph node status. Among these three variables, the ratio of the number of metastatic lymph nodes to the total number of dissected lymph nodes was the most meaningful prognostic factor.