DNA-based vaccines were employed to assess protective immunity against herpes simplex virus in experimental infections of hairless (strain SKH1) and BALB/c mice. Mice were vaccinated with plasmids containing the herpes simplex virus type-1 (HSV-1) glycoprotein B (gB) or D (gD) genes under the human cytomegalovirus immediate-early promoter control. Vaccines were injected intramuscularly (i.m.) or intraperitoneally (i.p.) as purified DNA alone or as formulations supplemented with different non-ionic block copolymers. Antibody responses were assessed by immunofluorescence and radio-immunoprecipitation assays. Mice inoculated with either gB or gD plasmid, alone or with non-ionic block copolymers CRL 1029 and CRL 1190, produced high levels of antibodies specific for gB or gD. Three weeks after the last vaccination, mice were challenged with a clinical HSV-1 isolate (ABGK-1) by inoculation of a shaved and subsequently scarified area between the third and fourth lumbar vertebrae. Mice immunised with either gD or gB plasmid alone or mixed with copolymers were protected against lethal HSV-1 challenge when immunisation was performed via the i.m. route. Immunisations given via the i.p. route induced humoral responses in some mice and protected the animals against lethal HSV-1 challenge only when the formulations contained copolymers. The BALB/c mouse model was shown to be as good a model as the hairless mouse model.