Relationships among cell-mediated immune (CMI) responses, neutralizing antibody, and macrophages in host resistance to vaginal or systemic infection with HSV-2 were defined in BALB/c mice. The importance of T-lymphocytes in resistance to either systemic or vaginal infection was demonstrated by increased susceptibility of mice depleted of T-lymphocytes. A role for non-specific resistance against the systemic, but not vaginal, infection was demonstrated by increased susceptibility of mice depleted of macrophages. The temporal relationships among the serum antibody response, and the delayed-type hypersensitivity (DTH) and splenic proliferative CMI responses were defined in individual animals. Vaginal infection was associated exclusively with relatively transient CMI responses which appeared during the acute infection. After systemic infection, CMI responses appeared during the acute infection. After systemic infection, CMI responses appeared during the acute infection and persisted for approximately five weeks, while a humoral response appeared in surviving animals and persisted for at least four months. The results suggest that CMI is the predominant host response to vaginal HSV-2 infection, while both CMI and macrophage-mediated antiviral activity may be involved in recovery from primary systemic infection with HSV-2.