Glycyrrhizin (GL) is a saponin widely used as an anti-inflammatory agent. Pain intensity and HLA-DR antigen expression on CD8+ cells were assessed during and after treatment with GL. Other agents such as acyclovir,γ-globulin and interferon β were also administered for comparison. Pain resolved most rapidly among those treated with acyclovir followed by those treated with GL. Pain resolution correlated with the regression of HLA-DR+ in CD8+ subpopulations in peripheral blood. GL is suggested to be an alternative or additive antiviral agent to herpes zoste