Light and electron microscopic changes in human liver cells which were considered to be precancerous lesions, were studied. In our micrometrical examination, dysplastic liver cells were classified into two types: large and small dysplastic cell. Each type had nuclear pleomorphism and multinucleation; however, the nucleocytoplasmic ratio of the large dysplastic cell remained normal. Electron microscopically, the large dysplastic cell had some features of regenerative cells. The nucleocytoplasmic ratio of the small dysplastic cell was between that of normal hepatocytes and liver cancer cells. The difference in the incidence of the small and large dysplastic cells in normal livers and cirrhotic livers having hepatocellular carcinoma was statistically significant. In addition, the small dysplastic cell had more of a tendency to produce a small round focus. It was morphologically suggested that the more important candidate for the precancerous cell in the liver was the small dysplastic cell.