Background: Contact immunotherapy has been shown to be effective for warts. Two previous studies on the use of squaric acid dibutylester (SADBE) for warts have reported widely divergent cure rates (10% and 60%). Objective: Our purpose was to determine the efficacy of SADBE in the treatment of recalcitrant warts. Methods: We treated 29 patients with SADBE for warts that were resistant to other therapies. The patient population had warts for a mean duration of 2.1 years. Patients were sensitized with 1% or 2% SADBE in acetone under occlusion, then treated with 0.5% to 5% SADBE applied to their warts every 2 to 4 weeks in the office. Results: Clearing of all warts was seen in 20 of 29 patients (69%), improvement in 3 patients (10%), and no change in 6 patients (21%). For the cured patients, mean duration of treatment was 4.2 months (range, 1 to 12 months) and mean number of treatments was 5.7 (range, 2 to 15). Adverse effects included acute contact dermatitis with 6 patients experiencing blisters and one experiencing hypopigmentation. Conclusion: SADBE treatment is worth considering in patients with recalcitrant warts, especially in those who tolerate painful procedures poorly.