The effect of budesonide, 1, 2, and 4mg/l00ml in daily enemas, on active distal ulcerative colitis was compared with that of prednisolone disodium phosphate enemas, 25 mg/100 ml, in a multicentre, randomized, group-comparative trial. A total of 146 patients with active disease were treated for 2 weeks. Data from 139 were valid for statistical analyses. Bowel habits, proctoscopy findings, and histologic pictures were evaluated, and plasma Cortisol was determined for measurement of influence on the hypothalamic-pituitary-adrenal axis. Clinical symptoms and proctoscopy findings improved within all treatment groups. The improvement of these effect variables tended to be less after treatment with the lowest dose of budesonide, 1 mg/100 ml, than after the other treatments. Plasma Cortisol did not change in any of the budesonide groups, whereas a mean reduction of 30% (P = 0.07) was observed after prednisolone. It can be concluded that budesonide enemas of 2 mg/100 ml constitute an attractive alternative to prednisolone enemas for topical treatment of distal ulcerative colitis.