44 patients with multiple recalcitrant warts were treated with weekly applications of diphencyprone. 20 patients were cured completely and 17 improved with reduction in the number or dimension of warts. Plantar warts responded less satisfactorily. Sensitization is not always tolerated by patients and the risk of eczema spreading to other sites must be considered. However, topical immunotherapy has to be considered as an alternative means of treatment in selected patients. The mode of action is discussed.