The authors studied 93 patients who had undergone curative resection for advanced gastric cancer to assess the prognostic significance of DNA ploidy in relation to patient age. The cancers were classified as low and high-ploidy carcinomas and the patients were grouped by age (22-44 years, 45-64 years, 65-79 years). The incidence of high ploidy cancers increased with age. The 5-year survival rate increased with patient age in the low ploidy group whereas it decreased with patient age in the high ploidy group. There was a statistically significant difference (P less than 0.05) in the 5-year survival between our oldest patients with low (100%) and high ploidy (25.7%) gastric cancer. High ploidy cancers manifested a higher incidence of vessel invasion and lymph node metastasis. Our findings indicate that analysis of the DNA distribution pattern in gastric carcinoma is of prognostic value especially in older patients.