Objective To verify whether there is intratumoral heterogeneity of DNA ploidy pattern in hep- atocellular carcinoma.Methods Using paraffin-embedded specimens resected from 29 patients with untreated hepatocellular carcinoma (HCC) and having undergone partial hepatectomy,DNA ploidy was analyzed at different sites of the same HCC by means of flow cytometry.Results There was no case in which diploid and aneuploid HCCs cells coexisted in the same tumor.The DNA ploidy pattern was diploid in 13 and aneuploid in 16 cases.A- mong 16 aneuploid tumors,the DNA indices at different sites were similar in 9,but different aneuploid subclones coexisted in 7 cases.Conclusions It is suggested that aneuploid subpopulation from diploid is rare,but new ane- uploid subclones could evolve from aneuploid HCC due to increased instability of their karyotype.