Data are reported on the HSV nonstructural antigens detected in GPK and RK cells after infection with the same strain of virus. Both the HSV types 1 and 2 NV antigens consist of more than one component for which the immunized guinea pigs produce distinct antibodies. It was possible to separate by PAGE, HSV-induced markers not only from cells undergoing lytic infection by the virus but also from viable cells from squamous cell carcinoma of the head and neck and the urogenital tract. These fractions were tested with sera from cancer patients, and the percentages of their CF reactivity are reported. The specificity of the antibody to the antigen from the cancer cells was less high than that of the antibody to the antigen from HSV-infected cells. It is suggested that the use of these PAGE separate antigens would eliminate the need for removal of the virion antibody from the cancer sera prior to testing them for the NV-specific antibody.