OBJECTIVE To evaluate the safety and immunogenicity of a recombinant glycoprotein vaccine for herpes simplex virus type 2 (HSV-2), which contains glycoproteins gD2 and gB2 combined with the novel MF59 adjuvant emulsion, in HSV-2-seronegative persons. METHODS Integrated summary of two phase I and two phase II studies. METHODS University and private outpatient clinics. METHODS 137 persons seronegative for HSV-2 antibodies as determined by HSV Western blot assay. METHODS Open-label vaccine administration with a dose-escalating design (phase I) was followed by randomized vaccine administration (phase II). Vaccine was administered intramuscularly into the deltoid at 0, 1, and 6 months. METHODS Neutralizing, HSV-2-binding antibodies and HSV-2-stimulated proliferative responses were measured before and after immunization. RESULTS Among HSV-seronegative patients, the gD2 and gB2 enzyme-linked immunosorbent assay (ELISA) and HSV-2-neutralizing antibody titers increased to levels equal to or higher than those seen in naturally acquired HSV-2 infection after the full three-dose immunization schedule. Among HSV-1-seropositive patients, one immunization produced increases in gD2 and gB2 ELISA antibody titers and HSV-2-neutralizing antibody titers that were 3 to 5 times greater than those in persons with naturally acquired HSV-2 infection. Among HSV-seronegative patients, frequency analysis assays showed a marked increase in the precursor frequency of gD2- and gB2-specific T cells after vaccination: T-cell responses after two immunizations were equal to the responses of HSV-2-seropositive patients and were sustained at day 180. The vaccine was well tolerated. CONCLUSIONS This subunit vaccine induces both humoral and cellular responses to HSV-2 that are equal to or greater than those of persons with naturally acquired HSV-2 infection. Studies to evaluate this vaccine for the prevention of genital herpes appear warranted.