To investigate the effects of common bile duct ligation in rat liver, 20 female Wistar Albinor rats were divided into 1 control and 4 experimental groups in which common bile ducts were ligated successively for 1, 2, 3 and 4 weeks.Electronmicroscopical investigation showed hepatocyte degeneration and fibrosis. We evaluated those morphological changes as follows : invaginations at hepatocyte nuclei, swollen mitochondria, fingerprint formation of hypertrophied granular endoplasmic reticulum within the hepatocyte cytoplasm, dense collagenous fibers at both the Space of Diss6 and portal triad. We concluded as those ultrastructural changes showed an augmentation with increasing ligation period.