Indirect immunofluorescence (IF), immunoperoxidase (IP) and seroneutralization tests were compared for detection and identification or Herpes simplex virus (HSV), directly in tissue smears or in cells inoculated with clinical materials. Detection and clear differentiation between the two HSV serotypes were obtained using rabbit immunoglobulin cross-absorbed with heterologous virus antigen. Immunofluorescent staining with specific monoclonal antibodies is as sensitive and more rapid than standard Vero cell cultures, for the laboratory diagnosis of HSV.