Artificial mixtures of the glycoproteins B, C, D, and E of herpes simplex virus 1 and 2 (HSV-1 and HSV-2),purified individually from infected Verocelllysates by immunoaffinity to monoclonal antibodies, were bound to an aluminum hydroxide gel and were used to immunize mice, guinea pigs, and owl monkeys (Aotus trivirgatus) once or twice (mice and guinea pigs) to as many as four times (owl monkeys). In all animals tested, low levels of neutralizing antibodies were detected only after two or more immunizations. Lymphocyte transformation tests in owl monkeys suggested low or borderline levels of cellular immunity. The survival of immunized mice after intracerebral challenge was inverselyrelated to the challenge dose. Immunized guinea pigs challenged by intravaginal inoculation showed reduced morbidity at the site of inoculation and were protected from CNS disease. Both immunized and nonimmunized monkeys were highly susceptible and could not be differentiated with respect to morbidity or mortality when challenged with 1,000 pfu of HSV-2 by the intravaginal route.