Commercially available mouse monoclonal antibodies to human IgG subclass (IgG1 to IgG4) were applied to an enzyme-linked immunosorbent assay to measure IgG subclass-specific antibodies to varicellazoster virus in children naturally infected with varicellazoster virus and in varicella vaccine recipients. In children naturally infected with varicella-zoster virus, IgG 1 antibody was detected 2 weeks after onset of the disease in all cases, its activity increased at 1 month after onset, and almost equal antibody value was maintained 10 years after infection. This pattern of antibody response was similar to that of total IgG antibody to varicella-zoster virus after natural infection. On the other hand, low antibody activity was found in IgG2 only at 1 month of the disease. The highest antibody level of IgG3 was shown 2 weeks after onset of the disease; then, it gradually decreased, and no antibody activity was detected 10 years later. IgG4 antibody was first detected 1 month after onset and an almost equal level of antibody was shown 10 years after the disease. After inoculation of children with a live varicella vaccine, in contrast, IgG subclass antibody responses to vaccine recipients were almost equal to those after natural infection.