This multicenter observational study examined the survival of 1420 patients with histologically proven carcinoma of the stomach. From April 1982 through October 1984, 1360 (95%) patients underwent surgery, 988 (72%) had resections, and 372 (28%) minor surgical procedures. The percentage of patients who have been followed until death or 3 to 5 years was 99.4%. Patients were staged preoperatively and intraoperatively and by pathologists using the old (1978) and new (1987) TNM stage groupings and 5-year survival was analyzed. Subgroups of patients who changed their stage group according to the new stage definitions were analyzed separately. Only age was an important prognostic factor for survival in Stage IA (P less than 0.05) and Stage IB (P less than 0.01). Residual tumor after surgery was most important for survival in Stage II (P less than 0.01) and Stage IIIA (P less than 0.001). This indicates that improvements of stage definitions for individual prognosis can only be achieved by adding data concerning the presence or absence of residual tumor (R classification).