Imiquimod is the newest in a class of drugs known as immune response modifiers. In preclinical studies, imiquimod induced the production of cytokines - the principal cytokine for antiviral activity being interferon alpha. Imiquimod does not inhibit viruses directly, nor does it cause direct, non-specific cytolytic destruction . Preclinical studies suggest that its antiviral action results from in vivo cytokine-induced activation of the immune system. This paper reviews a recent double blind, placebo-controlled study designed to evaluate this hypothesis. The results of this study showed that wart regression following treatment with imiquimod strongly correlated with a decrease in viral DNA and gene transcripts; a decrease in mRNA expression for proteins associated with cellular proliferation, and an increase in keratinocyte markers. These results support the hypothesis that stimulation of local cytokines by imiquimod leads to a reduction in human papilloma virus (HPV) load; to wart regression and to the normalisation of keratinocyte proliferation without evidence of scarring.