Cell nuclear DNA content was microspectrophotometrically measured in 60 specimens of clinical hepatocellular carcinoma (HCC). The DNA distribution pattern was classified into two types, diploid and nondiploid, according to the degree of dispersion on the DNA histogram. Among these 60 specimens, 26 had an HCC of less than 5 cm in diameter. In these 26, 17 (65%) had the diploid pattern and 9 (35%) had the nondiploid pattern. In the remaining 34 specimens with a large HCC exceeding 5 cm in diameter, the diploid pattern was seen in only six (18%), and the nondiploid pattern was seen in 28 (82%). Following increase in tumor size, the number of cases of nondiploid increased. The DNA pattern closely correlated with the morphologic grading and age of patients, yet there was no correlation among DNA pattern and presence of hepatitis B surface antigen (HBsAg) or presence of liver cirrhosis. Regarding the prognosis of patients with HCC, there was no statistic difference between DNA pattern and prognosis. The present study suggests that the DNA pattern relates to the biologic characteristics of the growth pattern of HCC. However, the DNA pattern showed no significant correlation with survival rates of patients with HCC who underwent hepatic resection.