The induction of a strong and long-lasting immunity characterized by both a humoral and cell-mediated immune (CMI) response is one of the most important considerations in developing an effective HIV vaccine. In previous studies, we have independently developed both DNA vaccine and macromolecular multicomponent peptide vaccine (VC1) candidates. In the present study, we attempted to optimize the vaccination protocol using mice, guinea pigs, rabbits and Macaca fuscata monkeys. Repeated vaccination with VC1 induced a substantial level of multivalent antibodies which neutralized various HIV-1 strains, as determined using a p24 inhibition assay. On the other hand, repeated immunization with DNA vaccine induced and sustained high levels of cytotoxic T lymphocytes (CTLs). In addition, when DNA vaccination was followed by multicomponent peptide vaccination, levels of both humoral immunity and CMI increased, and this effect continued for at least 10 months. These data clearly demonstrate that for inducing HIV-1 specific immunity, immunization with DNA vaccine followed by VC1 boosting produces better results than immunizing with either vaccine alone.