For 3 weeks, a 14-year-old boy had been aware of an enlarging lesion on the back of his hand. He recalled no trauma to the affected area. Further questioning by Dr D. Keith Cobb of Savannah, Ga, revealed that a 4-mm verruca, or wart, had been removed from the same site 6 months earlier with cryosurgery by a different physician. Warts are benign, epidermal tumors of viral origin that have an organized mosaic surface pattern. They are confined to the epidermis but can enlarge and displace the underlying dermis. This patient’s wart had been resistant to topical salicylic acid(Drug information on salicylic acid) preparations and to at-home currettage, treatments which often resolve the lesion. The inconsistent success of these measures may be linked to the patient’s immune response. The cryotherapy 6 months earlier resulted in temporary resolution. The verruca recurred when the virus spread to the periphery of the cryosurgically induced vesicle. Often, cryosurgery is an effective initial treatment; in this patient’s case, viral replication formed a wart larger in circumference than the original lesion. Because of the recalcitrant nature of the verruca, topical contact immunotherapy with dinitrochlorobenzene (DNCB) was prescribed. The use of this agent is controversial because of possible mutagenicity. This patient’s wart resolved completely after a few weeks of treatment with DNCB.