Large-cell liver cell dysplasia (LCD), suggested to be a preneoplastic change that progresses to hepatocellular carcinoma (HCC), has a reported frequency of DNA aneuploidy by flow cytometry intermediate between that of nonneoplastic liver (0%) and HCC (80%). We assessed DNA ploidy by image cytometry of Feulgen-stained 5-microns sections of 30 livers with LCD and of 60 HCCs (29 with LCD in adjacent nonmalignant liver). All 30 LCDs were aneuploid, 27 (90%) of which were multiploid--11 (41%) with hyperdiploid and hypertetraploid peaks. Forty-eight (80%) HCCs were aneuploid; in nine of 20 (42%) with a hyperdiploid peak, a hyperdiploid peak was also present in the LCDs, but in none was there less than 0.24 between DNA indices. Besides the 12 (20%) diploid HCCs, a diploid peak was present in four heterogenous, three multiploid, and six HCCs with two phenotypes and two genotypes, one of which was diploid. One aneuploid/hyperdiploid peak in each of 22 nonneoplastic and 24 cirrhotic livers did not have a corresponding LCD or HCC aneuploid peak. These data do not suggest that dysplastic hepatocytes form a single mutant clone that progresses to HCC.