Common warts, or verrucae vulgaris, occur most often in children. However, many adults are plagued by this ubiquitous viral infection. Various modalities have been used to treat warts, but none is uniformly effective or directly antiviral. A recent study showed cimetidine to be effective in the treatment of multiple warts in children. Anecdotal reports have suggested that the administration of high doses of cimetidine, through various proposed immunomodulating mechanisms, can improve recalcitrant warts in adults. There have been no data published to date supporting these claims.An open-label study was conducted to determine the safety and efficacy of high-dose cimetidine in 20 adult patients with recalcitrant warts. Of the 18 patients who completed the study, 16 patients (84%) had either dramatic clinical improvement or complete resolution of their wart lesions after 3 months of cimetidine therapy without any adverse effects. No patient demonstrated disease progression while receiving the medication and complete responders remained free of lesions at 1-year follow-up.This study further confirms that high-dose cimetidine therapy appears to be beneficial and safe in the treatment of recalcitrant warts in adults. Further placebo-controlled studies are needed to determine its true efficacy.