A total of eight patients with chronic active HBsAg-positive hepatitis was treated with recombinant interferon-alpha 2b for 12 months and serum aspartate aminotransferase, alanine aminotransferase, gamma-globulin and prolyl hydroxylase concentrations were determined every 3 months. Liver biopsies after 12 months' treatment revealed a significant (P less than 0.05) reduction in the histological activity score. After 6 months, alanine aminotransferase (P less than 0.01) and aspartate aminotransferase (P less than 0.05) concentrations fell significantly compared with baseline concentrations. Serum prolyl hydroxylase concentrations declined significantly (P less than 0.05) after 15 months and remained depressed. It is concluded that interferon-alpha 2b therapy reduced fibrogenetic activity in chronic active hepatitis B.