An indirect immunofluorescent antibody technique is described which can be used to identify rapidly, specifically and accurately herpesvirus hominis infections affecting the skin. The possible applications of this technique as a diagnostic aid of suspected herpetic infections in dermatology are illustrated and discussed. It is suggested that the method should prove useful in the investigation of all vesicular skin lesions in which infection with herpesvirus hominis is suspected. With the advent of anti-viral agents these techniques are likely to become increasingly important.