Liver biopsies from 18 patients with primary biliary cirrhosis (PBC) and from 25 patients with chronic active hepatitis (CAH) were stained by orcein after oxidation of the tissue sections with potassium permanganate. In 15 out of the 18 cases which could be classified on clinical, biochemical and immunological basis as PBC, the hepatocytes, usually periportally, contained cytoplasmic stainable material. 5 out of the 25 CAH patients contained the same material, but four of these patients were clinically atypical and showed features of cholestatic form of CAH and features crosslinking with PBC. All patients in both groups were serologically hepatitis-B antigen negative. The orcein staining method seems to be a reliable addition to differentiating histologically between PBC and CAH.