Nuclear DNA content of hepatocellular carcinoma (HCC) was estimated by flow cytometry after hepatic resection in 91 patients during the past 5 years. There were 53 diploid and 38 aneuploid tumours. Clinicopathological features were compared retrospectively between the patients with diploid and those with aneuploid HCC. DNA ploidy did not show any correlation with age, sex, alcohol abuse, hepatitis B virus, serum alpha-fetoprotein level or underlying liver disease. Histopathologically, the incidence of HCC less than 2 cm in diameter tended to be higher in the diploid group but no difference was seen for large tumours (greater than 5 cm). The grade of tumour differentiation also tended to be higher in this group of small HCC. The ploidy pattern did not influence the rate of capsule or daughter nodule formation, or venous invasion. There were no significant differences in survival rate or in the incidence and time of intrahepatic tumour recurrence between the two groups. This study may indicate that nuclear DNA ploidy is not a particularly predictive factor for the surgical treatment of HCC.