Immunization of rabbits with a soluble human liver fraction incorporated into Freund’s adjuvants produced antibodies that reacted with human liver extracts as well as extracts of other human organs. Absorption of the antihuman liver sera (AHLS) with lyophilized human serum, heart, and kidney abolished the reactions with other organs but did not remove the liver antibodies. The existence of at least two different liver antigens could be shown by gel diffusion precipitation experiments. One of these antigens could be removed by absorption of the antisera with chicken liver extracts. The AHLS did not cross-react with liver extracts of other species. Comparison of the AHLS with a mouse liver antiserum described previously indicated that these antisera detected closely related but nonidentical liver antigens. © 1977 S. Karger AG, Basel.