The correlation between DNA ploidy pattern and clinical outcome was studied in 76 patients with Borrmann type 4 gastric carcinomas. Twenty-six tumors were diploid, and 50 tumors were aneuploid. There was no correlation among DNA ploidy and histologic type, lymph-node status, wall invasion, or clinical stage. The incidence of vascular invasion in the aneuploid tumors was significantly higher than that in the diploid tumors. Five year survival was achieved in 28% of the patients with diploid tumors and 8% of those with aneuploid tumors, respectively. Among the patients undergoing curative resection, 5 year survival rate was 54% in the patients with diploid tumors compared to 28% with aneuploid tumors. There was a significant survival advantage in patients with diploid tumors. These results indicate that DNA ploidy might be an important prognostic factor in Borrmann type 4 gastric carcinomas.