Sensitive enzyme-linked immunoassays for herpes simplex virus (HSV), cytomegalovirus (CMV) and varicella-zoster virus (VZV) were developed. Both a sandwich technique, using antiviral antibodies from two species to detect the antigen, and an inhibition assay where the sample antigen was incubated with one antiserum, could be used. Around 4-50 ng of viral antigens (measured as protein content) could be detected. The ELISA inhibition technique using type-specific antisera could differentiate between HSV-1 and HSV-2 strains. These could also be distinguished in clinical samples. For CMV, both early and late antigens could be measured as well as the antigenic activity of CMV DNA polymerases. CMV activity in clinical specimens could be detected. The inhibition technique for VZV antigen determination appeared suitable for direct typing of clinical material. No cross-reaction with HSV was seen.