Systemic glucocorticosteroids have demonstrated efficacy in ulcerative colitis (UC) but cause undesired systemic side effects. Beclomethasone dipropionate (BDP) has potent topical activity and is extensively metabolized. This randomized double-blind study investigated an oral gastroresistant controlled-release preparation of BDP in 57 patients with mild to moderately severe extensive or left-sided UC. Patients were assigned to receive BDP 5 or 10 mg/d; a third group took a clinically inactive dose (1.6 g/d) of 5-aminosalicylic acid (5-ASA). Both BDP doses displayed excellent efficacy confirmed by results of endoscopy, biopsy, and clinical evaluation. Significant improvement from baseline occurred in most signs and symptoms of UC, particularly stool frequency, rectal bleeding, and mucus in the stool (P<.01). Tolerability was good in both BDP groups. Morning plasma cortisol levels decreased significantly from baseline with BDP 10 mg, but no significant changes in vital signs were observed at the end of treatment. Despite a small sample size and the open comparison with 5-ASA, this multicenter study showed the therapeutic equivalence of BDP 5 and 10 mg/d in alleviating clinical symptoms and improving endoscopic and biopsy scores in patients with mild to moderate UC. BDP 5 mg/d displayed better general tolerability and less reduction of plasma cortisol levels, however, and may be preferable to the higher dose in this indication.