Imiquimod is the first of a new class of drugs (immune response modifiers) to become commercially available. It is approved in many countries for the treatment of genital warts caused by the human papilloma virus infection. However, there are reports of its use in a variety of dermatological conditions, such as basal cell carcinomas, actinic keratoses, lentigo maligna, common warts and molluscum contagiosum. Its mechanism of action is through stimulation of the T helper cell Type 1 (Th1) immune response via activation of cell surface pathogen recognition receptors (mainly toll-like receptor 7). This activation stimulates the immune system's own defence mechanism against both virally infected and tumour cells. Imiquimod and other analogues show promise in the prophylactic treatment of skin tumours in some patients, especially those who are immunocompromised.