Microscopic colitis is an increasingly diagnosed cause of chronic diarrhea, with two main subtypes: collagenous and lymphocytic colitis. Uncontrolled reports have suggested that various drugs can be beneficial in treating microscopic colitis, but few treatments have been evaluated in randomized controlled trials. Thus, treatment is guided mostly by anecdotal reports, case series, and physicians' experience. In our uncontrolled experience, corticosteroids are one of the most effective therapies for microscopic colitis, but are not typically used as a first line therapy because of toxicity. Budesonide has been reported to be of clinical benefit in small, uncontrolled series of patients with microscopic colitis, and recent controlled trials showed that it is superior to placebo in collagenous colitis. We propose a study of budesonide in patients with the lymphocytic type of microscopic colitis.