Significant in the past several decades in developing attenuated live-virus vaccines for active immunization against a large number of viral diseases. There has been little success, however, in developing effective immunoprophylaxis against Herpesvirus hominis (HVH), and it is readily evident that repeated endogenous antigenic stimulation from reactivation of the latent infection does not prevent recurrent infection. The apparent inability to successfully immunize humans against HVH by vaccines may be the consequence of special features of defective host immunity or the result of unique biologic properties of the herpes simplex virus. Ineffective immunoprophylaxis against HVH appears to be related to three distinctive features of host-virus interrelations: (1) possible humoral, phagocytic, or cell-mediated dysfunction in the host with recurrent HVH1-9; (2) the special neurotrophic character and intraneuronal residence of HVH in a nascent, nonreplicative form,9-13 perhaps under influence of repressor genes14 or immunoglobulin modulation15; or (3) the special