Human liver has been homogenated and submitted to 150,000 g in order to investigate the supernatant for the presence of liver specific antigens. Gel-filtration on Sephadex G-100 revealed liver specific antigenicity in the first peak. Gel-filtration of the first peak on Sephadex G-200 revealed two peaks each exhibiting liver specific antigenicity. Immunochemical and physicochemical analysis made it possible to define the liver-specific antigen present in the first peak as a lipoprotein with the characteristics of a high molecular weight, low density protein. It is partly located in the membrane of liver cells. The liver specific protein of the second Sephadex G-200 peak has a molecular weight of about 190,000. It is located within the cytoplasm of hepatocytes.