As a result of Japanese reports of improved survival of gastric cancer patients after extended lymph node dissection, a study was undertaken to evaluate factors that might influence these results. The influence of staging was evaluated by stratifying 1085 patients of the National Cancer Center of Japan and grouping them according to the three commonly used systems; UICC's old and new TNM systems (fourth edition) and the system of the Japanese Research Society for the study of Gastric Cancer (JRSGC). No survival difference was found between the stages of the three systems, except for stage II, where the new TNM and the JRSGC differed (p < 0.05). In a second analysis, the incidence of the most important prognostic factors for advanced gastric cancer was compared among three institutions: the National Cancer Center Tokyo, Japan (NCC), the University Hospital Erlangen, Germany (UHE) and the University Hospital Maastricht in The Netherlands (UHM). Japanese patients were on average 3 years younger than the German patients and 8 years younger than the Dutch patients, and had a higher proportion of advanced (T4) carcinomas. Male-female distribution, histology, and lymph node invasion were comparable in the three groups. From these data a rather worse prognosis for Japanese advanced gastric cancer patients could be expected. However, the observed 5-year survival rates show a marked advantage for the Japanese patients: 57% (NCC) versus 34% (UHE) and 31% (UHM). The survival difference for stage II patients between the new TNM and the JRSGC staging systems is not sufficient to explain this advantage. This result underlines the importance of the Japanese therapeutic approach.(ABSTRACT TRUNCATED AT 250 WORDS)