Interferons are recognized to inhibit collagen production. Since fibrosis has been associated with liver dysfunction, we investigated the effects of alpha-interferon on the function and lipid composition of hepatocyte and erythrocyte plasma membranes derived from CCl4-cirrhotic male Wistar rats. In both cell types, CCl4 decreased Na+/K+ and Ca(2+)-ATPase activity and increased the cholesterol to phospholipids (CH/PL) ratio (p < 0.05). Administration of interferon (80,000 IU/kg s.c. for 8 weeks) increased survival from 40 to 90%, and preserved normal ATPase activity and CH/PL ratio. Our results show that administration of alpha-interferon to CCl4-cirrhotic rats improves survival, and liver and erythrocyte membrane function and composition, probably as a result of its antifibrogenic effect.