Hepatocellular carcinoma was induced in Sprague-Dawley rats using 2-Me DAB and DENA, and hepatoma associated antigens (HAA) were identified and isolated from the plasma membrane surface of rat liver. Rabbit antisera against HAA were obtained and reactivity of the antibody with proteins extracted from human livers (normal and hepatoma) was analyzed by double immunodiffusion, immunoelectrophoresis and crossed-immunoelectro-phoresis. The results showed a strong evidence for the presence of proteins (MW: 66,000 and 55,000) on the human liver cell cross-reacting with the antibody against rat HAA. These human proteins found to be unreactive with the antiserum against plasma membrane surface proteins of normal rat liver.