The imidazoquinoline, imiquimod, is a low molecular weight, synthetic immune response modifier that is used for the treatment of external genital and perianal warts. It is formulated in a 5% vanishing cream as Aldara. This self-applied therapy has shown good efficacy and safety in the treatment of external genital and perianal warts caused by human papillomavirus (HPV) infection. The antiviral mechanism of action of this compound is unlike any other approved antiviral therapy in that it induces the production of antiviral cytokines and cytokines that enhance cellular immunity believed to be necessary for the control or elimination of HPV infection. Imiquimod does not exert its antiviral effects directly on virus-infected cells. Treatment with imiquimod results in resolution of wart tissue and reduction of viral burden. Post-marketing trials using imiquimod demonstrated that patients who experience complete clearance of either new or recalcitrant warts tend to remain clear for longer periods as compared to other treatment modalities. Preclinical data demonstrate in vitro and in vivo that imiquimod directly induces antiviral and immunomodulating cytokines from monocytes, macrophages and dendritic cells. These immunomodulating cytokines have been shown to potentiate Th1 immunity. Self-application, good tolerability, a unique mechanism of action and a relatively high sustained clearance rate combine to make imiquimod a cost-effective first-line therapy for external genital warts and an appropriate second-line therapy when other treatments are unsuccessful. In small-scale studies requiring replication, imiquimod has also been shown to be effective in the treatment of non-HVP-related skin infections and some dermal neoplasias.