Karyometry of hepatocytes was performed on 68 autopsy cases including cirrhosis with and without hepatoma and control, in order to relate the premalignant state of liver to the corresponding cellular changes. On thick liver sections, nuclei of hepatocytes or of hepatoma cells were subjected to measurement of nuclear diameter, in which the following parameters were employed; the mean D and deviation s of D, the numerical density of nuclei Nv and N/C ratio, tne eccentricity e² of nuclear shape was also calculatied by simulating nuclear sections with dllipses. Hepatoma itself was characterized by elevated s, e², Nv and N/C, of which the former three denote size unequality, transformation into an elongated shape, and elevated density of hepatoma cell nuclei, respectively. Comparison of hepatocytes between cirrhotic and control cases disclosed that in cirrhosis, nuclei were rather more uniform and less atypical with even lower N/C than in control, a change that was remote from the findings in hepatoma cells. This is not consistent with the morphology of premalignant cells in an ordinary sense. On the other hand comparison between cirrhotic groups with and without hepatoma revealed, a significant increase in Nv and N/C of hepatocytes in the group with hepatoma, suggesting that canceration was preceded by hepatocellular hyperplasia which produced mass of unusually small cells.