Estradiol benzoate (EB), a synthetic estrogen, was injected to macronodular cirrhotic rats, and the reversibility of the lesion was investigated. Macronodular liver cirrhosis (MNLC) was produced by use of carbon tetrachloride plus 3'-Me- DAB. In animals with no treatment, regenerative nodules remained unchanged during an eighteen-week observation period. Microangiograms showed mark edly deranged intrahepatic microvasculatures, including an irregularly con toured vascular tree and rarefaction in the peripheral area. On the other hand, EB treatment exerted conspicuous efficacy on the above-mentioned intrahepatic microcirculatory disorder and on sinusoidal dilatation, which led the livers with MNLC to revert to almost normal appearance. It is concluded that EB provides a salutary effect on the intrahepatic microcirculatory system, by means of which MNLC can be shown to be a reversible lesion.