Evidence for new antigenic specificities in Australia antigen positive sera, for one of which we have proposed the designation e, has been obtained in immunodiffusion tests according to Ouchterlony. These specificities co-occur with Au antigen and are distinct from the a, d, y and x determinants of the Au antigen complex according to Le Bouvier and occur on particles other than those carrying the a determinant. It was found in 18 out of 23 persistent carriers of Au antigen from hemodialysis units, in 6 out of 43 Au positive hepatitis cases but in none of 17 Au antigen-carrying blood donors. In the latter group, however, antibodies against the specificities described herein occurred in 13 out of 17 individuals. In five of these cases the antibody was directed against the e specificity. Some evidence is presented for the possible association of this antigen complex to contagiousness.