We are using genetically modified, conditionally replicating herpes simplex virus (HSV) that express either interleukin (IL)-12 or granulocyte macrophage-colony stimulating factor (GM-CSF) as live, attenuated vaccine candidates for protection against HSV infection and/or disease. We report the following: (1) animals previously vaccinated with these candidate vaccines exhibited dose-dependent protection after intranasal, intraperitoneal or intracranial challenge with the highly virulent E377-MB wild-type HSV-1; (2) the IL-12 expressing virus (M002) consistently conferred protection at lower immunization doses than GM-CSF expressing virus (M004); (3) between 80 and 100% protection from E377-MB challenge was conferred after intramuscular immunization of mice with any of the three Deltagamma1 34.5 HSV, as opposed to 50% protection elicited after immunization with wild-type HSV-1 (F); and (4) latent virus was not detected at a higher rate in animals immunized and subsequently challenged with E377-MB than in immunized animals alone. These data suggest that conditionally replicating, cytokine-expressing HSV are able to elicit protective immune responses while retaining safety in an experimental murine model.