Herpes viruses are responsible for a wide spectrum of infections ranging from cold sores, genital herpes, and chicken pox to disseminated herpes infections in normal and more commonly in immunocompromised patients. Symptoms range from mildly distressing and uncomfortable to severe and life-threatening. The sophistication of virological methods is increasing. Specific types, classes, and subclasses of antibodies to viruses can now be determined, as well as the reactivity of T-lymphocytes. It is possible to detect herpes virus type-specific antibodies (to HSV-l or HSV-2) in a blood sample using the simple and inexpensive enzyme-linked immunosorbent assay (ELISA). The virus is usually type-determined rapidly and currently susceptibility or resistance to antiviral compounds can be defined in vitro. Such assays of antiviral resistance have been shown to be quick and effective. Effective antiviral therapies have been developed against a number of viral diseases. The concomitant need for isolation and evaluation of resistance patterns of herpes virus against different antiviral compounds appears to be of considerable importance. Pure clinical observations are no longer sufficient to distinguish the types, since HSV-l may be present in the genital region and HSV-2 at upper parts of the body–contrary to common belief.