The immunotherapeutic potential of a monoclonal antibody specific for glycoprotein D of herpes simplex virus was evaluated in a murine ocular infection model. Passive transfer of antibody at microgram concentrations was able to promote resolution of corneal opacity and hasten healing of blepharitis. Antibody treatment did not prevent development of either a cellular or humoral antiviral immune response. In fact, kinetic studies revealed that the early delayed-type hypersensitivity response was significantly more vigorous in the treated group than in the controls. Potential explanations as to how a single microgram inoculation of antibody could exert a therapeutic effect are discussed.