The structural proteins of Herpesvirus saimiri strains 11 and 11 att and of Herpesvirus ateles strains 73 and 810 were characterized by electrophoresis in SDS-polyacrylamide gels. For H. saimiri 21 virus structural proteins could be identified with molecular weights ranging from 28,000 to 210,000 Da. For H. ateles 810 and H. ateles 73, 20 polypeptides were characterized. Using lactoperoxidase for iodination of surface proteins and immunoprecipitation, 5 polypeptides could be identified as envelope and 4 as capsid surface proteins.