Clinical, biochemical and immunological variables were analyzed in 30 patients with orcein-negative (ON) chronic active hepatitis (CAH), 4 patients with ON primary biliary cirrhosis (PBC), 8 patients with orcein-positive (OP; intracellular copper-binding protein seen histologically in liver biopsy specimens) CAH and 15 patients with OP-PBC. A marked elevation of serum bile acids, alkaline phosphatase, leusine aminopeptidase, gammaglutamyl transpeptidase and cholesterol concentrations, and highly pathological BSP Tm values were characteristic for OP-cases. In addition the faecal fat level was increased and bile acids decreased in OP-cases. Serum levels of IgG or IgM and the occurrence of smooth muscle, mitochondrial or glomerular antibodies were identical in ON- and OP-CAH as well as also in ON- and OP-PBC. 49 patients were treated with a combination of prednisone and azathioprine from 4 to 72 months (mean 22). 26 patients with ON-CAH responded biochemically and morphologically to the treatment. No treatment failures were found in ON-CAH. In contrast treatment failure was confirmed in every treated OP-PBC or OP-CAH. The results suggest that orcein-positivity indicates a poor response to prednisone-azathioprine treatment of CAH.