Background & Aims: Budesonide is effective in treating collagenous colitis, but no treatment is established for lymphocytic colitis. We performed a randomized, double-blind, placebo-controlled study to evaluate the effects of budesonide in patients with lymphocytic colitis. Methods: Forty-two patients (median age, 61 years) with lymphocytic colitis and chronic diarrhea were randomly assigned to groups that were given oral doses of budesonide (9 mg/d) or placebo for 6 weeks. Nonresponders at week 6 were given open-label budesonide (9 mg/d) for 6 additional weeks. A complete colonoscopy and histologic and quality-of-life analyses were performed at baseline and at week 6. The primary end point was clinical remission at 6 weeks, with last observation carried forward (LOCF). All patients who left the study in clinical remission were followed for relapse. Results: At week 6, 86% of patients given budesonide were in clinical remission (with LOCF) compared with 48% of patients given placebo (P = .010). Furthermore, open-label budesonide therapy induced clinical remission in 7 of 8 patients given placebo. Histologic remission was observed in 73% of patients given budesonide compared with 31% given placebo (P = .030). Only 1 patient discontinued budesonide therapy prematurely. During a mean follow-up period of 14 months, 15 patients (44.1%) experienced a clinical relapse (after a mean of 2 months); 8 of the relapsing patients were retreated with and responded again to budesonide. Conclusions: Budesonide effectively induces clinical remission in patients with lymphocytic colitis and significantly improves histology results after 6 weeks. Clinical relapses occur but can be treated again with budesonide.