Background: Ulcerative colitis is predominantly a disease of nonsmokers. Transdermal nicotine may help control clinical manifestations of this condition. Objective: Tb determine the efficacy of transdermal nicotine for controlling clinical disease activity in active ulcerative colitis. Design: Randomized, double-blind, placebo-controlled, single-center clinical trial. Setting: Multispecialty group serving as an academic tertiary referral center. Patients: 64 nonsmoking patients with mildly to moderately active ulcerative colitis despite the use of medication. Intervention: Patients were stratified on the basis of smoking history, extent of disease, and concomitant medical therapy. After stratification, patients were randomly assigned to daily treatment with transdermal nicotine (n = 31) at the highest tolerated dose (11 mg for 1 week and then less than or equal to 22 mg for 3 weeks) or placebo (n = 33). Measurements: Clinical features were assessed at baseline and 4 weeks by endoscopy, physician assessment, and a patient diary of daily symptoms. Serum concentrations of nicotine were determined by using gas chromatography and mass spectrometry, and plasma concentrations of cotinine were measured by using high-performance liquid chromatography. Results: At 4 weeks, 12 of 31 patients (39%) who received nicotine showed clinical improvement compared with 3 of 33 patients (9%) who received placebo (P = 0.007). Four patients receiving nicotine discontinued therapy because of side effects (contact dermatitis [n = 2], nausea [n = 1], and acute pancreatitis [n = 1]). At week 4, the nicotine group had a mean (+/-SD) trough serum nicotine concentration of 12.3 +/- 8.4 ng/mL and a mean trough plasma cotinine concentration of 192 +/- 95 ng/mL. Conclusions: Transdermal nicotine administered at the highest tolerated dosage (less than or equal to 22 mg/d) for 4 weeks is efficacious for controlling clinical manifestations of mildly to moderately active ulcerative colitis.