Background and aim: Treatment of resistant warts is a common clinical problem. Immunotherapy with diphenyl cyclopropenone (DCP) as a contact sensitizer has been reported. The objective of this study was to evaluate the efficacy of DCP in refractory warts.Materials and methods: Nineteen patients with refractory warts referred to Razi Hospital in 2004 who had not responded to at least 2 treatment modalities, were sensitized with 2% DCP in acetone.Then treatment was started with application of 1% DCP on plantar warts and 0.2% on other locations.Results: Two patients were not sensitized even after 3 attempts. Three other patients discontinuedtreatment due to side effects (severe eczema and pruritus). Six male and 8 female patients completed the trial, among them,10 (71.5%) showed complete clearance of warts. Side effects reported were: local pruritus (21%), distant eczema (10.5%), local blister (26.3%). The patients received a mean of 5 treatment sessions.Conclusion: Topical immunotherapy with DCP is an effective treatment for refractory warts. Due to high efficacy, no scarring, and being a painless procedure it can be considered as a first line treatment of refractory warts.