Three young dogs with a history of apathy, anorexia and weight loss were presented with severe ascites. Abnormal laboratory findings include hypoalbuminaemia and increased activities of alkaline phosphatase, serum aspartate amino-transferase, serum glutamic pyruvic transaminase and gamma-glutamyl transferase. Ammonia tolerance was also abnormal. At autopsy ascites and peripheral portosystemic collaterals were found. The livers were abnormally small and firm and their surfaces were irregular. Histologically, there was marked periportal fibrosis, increased numbers of bile ductules and arteriolae in the portal areas and an absence of normal portal vein tributaries. No inflammatory changes were found. These lesions are discussed in relation to the various causes of hepatic fibrosis.