In this study the DNAs of the neurotropic human herpes viruses will be characterized, particularly with regard to latent infection in the human trigeminal ganglion. Two questions that will be addressed are: (1) can herpes simplex virus and varicella-zoster virus DNAs be found in the same trigeminal ganglion? (2) can herpes simplex virus and varicella-zoster virus RNAs be found in the same neuron? In addition, the oral and venereal strains of herpes simplex virus will be compared on the basis of DNA sequence homology by the completion of the heteroduplex map. For varicella-zoster virus, the apparently defective DNA of a live, attenuated varicella vaccine strain will be compared in detail to the DNA of the parental wild-type isolate. The DNAs of the parental and vaccine varicella-zoster viruses will be tested for the ability to transform cells in culture. All these studies are related and are of immediate relevance to human health. Herpes simplex virus causes widespread oral and venereal infections in the Human population and may be part of the causation of human cervical cancer. Varicalla-zoster virus causes an ubiquitous, highly contagious disease of childhood, chicken-pox, as well as a painful disease of the elderly of immunocomprised patients, shingles.