Interferons have been used to treat chronic hepatitis owing to their antiviral properties. However, now interferons are recognized to inhibit collagen production. Because fibrosis has been associated with liver damage and disfunction, the effects of interferon-α2b on biliary obstruction-induced cirrhosis were investigated. Obstructive jaundice was induced in male Wistar rats (ca. 200 g) by double ligation and division of the common bile duct. Control rats were sham operated. Interferon-α2b (IFN-α; 100 000 IU per rat) was administered subcutaneously daily after surgery. The animals were sacrificed after 4 weeks of bile duct ligation (BDL) or sham operation. Bilirubins and serum enzyme activities of alkaline phosphatase and γ-glutamil transpeptidase (determined as markers of liver damage) increased several-fold after BDL. Erythrocyte and hepatocyte plasma membrane Na+/K+- and Ca2+ -ATPase activities decreased significantly in the BDL group. Administration of IFN-α to BDL rats resulted in a partial normalization of serum markers of liver damage. The normal activity of both ATPases on erythrocyte and hepatocyte plasma membranes was completely preserved by IFN-α. It is concluded that interferons possess interesting hepatoprotective effects not related to their antiviral properties but probably associated with their antifibrogenic effect.