A technique for simultaneous specific lymphocyte proliferation and IgG production with herpesvirus antigens in solid phase was developed. The cell mediated immune response was highly specific. Stronger cellular responses were found after stimulation with nucleocapsid antigens than with membrane antigens. Varicella-zoster virus (VZV) and herpes simplex virus (HSV) specific antibody production in vitro were found in almost 100% of seropositive individuals, while cytomegalovirus (CMV) antibody production was detectable in 70%. A higher specific IgG production was found after stimulation with CMV and VZV membrane antigens than with CMV nucleocapsid and VZV cell antigens. No differences in IgG production were found with the two types of HSV antigens. A method for viral IgG subclass determination in vitro was also developed. These methods may be used for monitoring immunosuppressed patients for immunological responsiveness to herpesvirus infections.