SH virus-associated antigens have been identified in the liver and blood by immunofluorescence. This antigenic expression of the hepatitis agent or its genome is found in the cytoplasm of hepatocytes and other cells of the liver. Acute hepatitis is associated with hepatocellular localization of SH antigen, whereas alternative or additional SH antigen in the cytoplasm of nonhepatocytes is observed in chronic or recurrent hepatitis. Persistent intrahepatic SH antigen has also been observed in conversion from acute to chronic hepatitis, and the persistence of this virus-associated antigen in the liver may serve a significant pathogenetic role in mediating direct anti-tissue responses as well as local immune complex reactions. Competitive inhibition studies of SH antigen suggest at least two antigenically and sterically independent determinants on the SH particle.