Between November 1990 and December 1992, 217 patients with stomach cancer were enrolled in a prospective study evaluating the prognostic value of DNA flow cytometry. Laurén's histological type was evaluated in 216 cases, of which 102 (47%) were of the diffuse type, 74 (34%) were of the intestinal type, and 40 (19%) were mixed type tumors. Laurén's histological type showed a significant correlation with age (p = 0.028), sex (p = 0.004), tumor size (p = 0.002), T stage (p = 0.006), overall TNM stage (p = 0.008), histological grade (p < 0.001), and tumor ploidy (p < 0.001). Intestinal type stomach cancer showed a significantly higher proportion of aneuploidy [diffuse vs. intestinal type; 41/102 (40%) vs. 52/74 (70%)]. After a median follow-up of 66.1 months (range, 29.6-78.1), 110 of 216 patients (51%) survived. Patients with intestinal type stomach cancer had a significantly better survival than did those with diffuse type stomach cancer (64% vs. 42% of patients surviving, p = 0.020). Our study suggests that there are biological differences between the two subtypes of Laurén's classification of stomach cancer in addition to the morphological differences. Laurén's classification should remain valid in future studies investigating the pathogenetic and clinical aspects of stomach cancer.