SUMMARYAim: To evaluate efficacy and safety of oral beclometasone dipropionate (BDP) when added to 5-ASA in the treatment of patients with active ulcerative colitis. Methods: In a 4-week, placebo-controlled, double-blind study, patients with extensive or left-sided mild to moderate active ulcerative colitis were randomized to receive oral 5-ASA (3.2 g ⁄ day) plus BDP (5 mg ⁄ day) or placebo. Clinical, endoscopic and histologic features, and haematochemical parameters were recorded at baseline and at the end of the study. Results: One hundred and nineteen patients were enrolled and randomly treated with BDP plus 5-ASA (n ¼ 58) or placebo plus 5-ASA (n ¼ 61). Both treatment groups showed a statistically significant decrease of disease activity index (DAI) and histology score at the end of treatment (P ¼ 0.001, each). DAI score was lower in the BDP group than in the placebo group (P ¼ 0.014), with more patients in clinical remission in the BDP group (58.6% vs. 34.4%, P ¼ 0.008). Serum cortisol levels significantly decreased in BDP group vs. baseline (P ¼ 0.002), but without signs of pituitary-adrenal function depletion. A low incidence of adverse events was observed in both groups. Conclusions: Oral BDP in combination with oral 5-ASA is significantly more effective than 5-ASA alone in the treatment of patients with extensive or left-sided active ulcerative colitis.