BACKGROUND: Budesonide is a new corticosteroid with high topical anti-inflammatory activity but little systemic effect. The aim of the present study was to compare the efficacy and safety of budesonide enema (2 mg/100 mL) and 5-ASA enema (mesalazine 1 g/100 mL) given for 4 weeks in the treatment of active distal ulcerative colitis and proctitis. METHODS: Ninety-seven patients were studied in a multicentre single-blind randomized group-comparative trial. The primary efficacy variables were endoscopy and histopathology scores obtained at 0, 2 and 4 weeks. Clinical symptoms were the secondary efficacy variables. Haematology, chemistry and adverse events were the safety variables. RESULTS: Budesonide and 5-ASA enemas both resulted in a significant improvement in endoscopy and histopathology scores but no difference could be demonstrated between the two treatment groups. There was also a significant improvement of symptoms (number of bowel movements per day, quality of stools, presence of blood and mucus, and state of well-being) within both groups but no difference between the two treatment groups. The clinical remission rate at 4 weeks was, however, 38% for patients treated with budesonide enema but 60% for those treated with 5-ASA enema (P = 0.03). No adverse events attributed to the study drugs were recorded in either of the groups. CONCLUSIONS: Budesonide enema 2 mg/100 mL appears to be as efficient and well-tolerated as 5-ASA enema in the treatment of active distal ulcerative colitis and proctitis.