The extrahepatic common bile ducts (CBD) of 24 wistar strain rats were ligated distal to liver. Two rats from the above batch of animals were slaughtered 1,2,3,4,5,6,7,9,12 and 15 days after the ligation surgery. Pieces of liver and CBD were fixed and prepared for section cutting, each day. A control batch of sham operated rats was likewise proceeded on the above experimental days. Gross observations of experimental (with ligated CEO) rats showed a continuous increase in the size of liver, dilatation of biliary tree, and ginge of jaundice in the ears proportional to the time of cholestasis. The following changes were observed in the histological structure of liver. (1) The portal area (PA) expanded gradually during the post-ligation period, which may be attributed to oedema on the first and second post-ligation day, and proliferation of connective tissue and biliary duct epithelium from the second post-ligation day onwards. In control rat the PA measures 0.063+0.015 mm (n = 10), while that of the 7th post-ligation day measures 0.317+0.18 mm (n = 10). The number of bile ducts (ED) per portal area likewise, increased during the post-ligation period. The number of BD/PA increased to 19+5 (n = 10) on the 7th postligation day, as compared with 1.4+0.4 (n 10) BD per PA of control liver. The increase in the size of PA and the corresponding increase in the number of BD was so extensive on the 9th post-ligation day and afterwards that no accurate counting or measurements could be done. (2) Signs of degeneration, as indicated by the presence of balloon cells (=hepatocytes having hydropic and granular degeneration in the cytoplasm), and regeneration, as indicated by the presence of mitotic figures, in the parenchyma were observed. The degenerative changes seemed to dominate over regenerative changes. The bile canaliculi dilatation and Disse spaces, which became visible on the 3rd post-ligation day, appeared to have developed a communication with one another. The ectopic biliary epithelium nests, surrounded by connective tissue and unrelated with blood vessels, were seen in the parenchyma on the 5th postligation day. Some groups of liver cells, surrounded by connective tissue, were observed on the 15th post-ligation day. (3) The connective tissue increased in magnitude, proposal to the post-ligation period. On the 9th post-ligation day and onward. the fibrous strands extended from one portal area to the other And also invaded the parenchyma. (4) The internal epithelium of common bile duct was gradually flattened and the folds got straightened vat. The mucus glands gradually diminished. The thinning of epithelial wall, which was pronounced at the places of sacculation, was accompanied by its increasing compactness.