DNA content was quantitatively determined in 38 hepatocellular carcinoma (HCC) by image analysis technique using paraffin-embedded sections stained with Feulgen method. The results showed that diploid/near diploid DNA content (D/ND) and aneuploid DNA content (AN) were found in 15.8% and 84.2% of HCC. The incidences of tumor capsule invasion and cancerous thrombus formation were 84.4% and 87.5% in AN HCC which are significantly higher than in D/ND HCC (33.3% and 50%) (P less than 0.05). The tumor size of HCC was related to DNA content, 66.7% of D/ND HCC was less than or equal to 3 cm in diameter, whereas 75% of AN HCC was greater than 3 cm across (P less than 0.05), suggesting that HCC at 3 cm in size may be a critical point at which the biologic characteristics of HCC would change. There was no correlation between the DNA content and pathologic grading of HCC. It is suggested that the development of AN stem line with a broad distribution of DNA content be an important biologic marker of HCC with increased malignancy and the quantitative analysis of DNA content be able to provide an objective and quantitative reference for evaluating the biologic characteristics. The above observation may be taken as a valuable supplement to the pathologic grading of HCC.