Radioligand and immunohistochemical analysis was used for studying the expression of an unusual estrogen-binding protein (UEBP) in the regenerated liver of male rats poisoned with CCl4. As a result of CCl4 poisoning, most hepatocytes intensely producing UEBP and located in the central part of the liver lobules are destroyed (40 to 90% of the liver parenchymal cells). Dead cells are substituted by new hepatocytes formed due to proliferation of periportal hepatocytes in which UEBP is expressed at a low level. In regenerated liver, however, a high level of UEBP expression characteristic of the control animals is restored, as well as a gradient mode of distribution of UEBP-containing cells with the maximum UEBP concentration in hepatocytes surrounding the central vein. The results obtained with animals with either intact or removed testes were similar, except that the dynamics of liver regeneration was slower in the castrated rats. These data suggest the existence in all hepatocytes of the complete androgen-related program for UEBP expression. This program is inherited by daughter cells in the absence of an inducing hormone and is similar in all cells, independently of the extent of its phenotypic expression in hepatocytes with different localization within the liver lobule.