ABSTRACT— Intracellular, eosinophilic, hyaline inclusions (alcoholic hyalin, Mallory bodies) are found in livers of patients with a number of hepatic disorders, although they are most common in alcoholic liver disease. Tissues from patients with primary biliary cirrhosis, jejunoileal bypass, hepatocellular carcinoma, Wilson's disease, and Indian childhood cirrhosis were all positive for hyalin by hematoxylin and eosin staining. Immunocytochemical labeling, using guinea-pig antiserum specific for alcoholic hyalin, was utilized to determine the extent of crossreactivity between hepatocellular hyalin in these various conditions. This antiserum bound to hyalin in fixed paraffin-embedded sections of all liver tissues studied as detected by indirect immunoperoxidase labeling. Binding to normal human liver, however, was restricted to light staining at the surface of hepatocytes. Preimmune guinea-pig serum did not bind to either normal liver or to the test tissues. Our results suggest that hyalin found in a diverse group of liver conditions represents an immunologically related structure and that its formation may involve a common mechanism.