Objectives. Budesonide is a corticosteroid with low systemic bioavailability because of its high first-pass metabolism in the liver. In this paediatric, randomized, double-blind, double-dummy, controlled, multicentre trial, the safety and efficacy of budesonide versus prednisolone were evaluated in children with active Crohn's disease. Methods. Forty-eight children, aged 6-16 years, with active Crohn's disease (Crohn's Disease Activity Index > 200) involving ileum and/or ascending colon were randomized to receive budesonide (9 mg/day for 8 weeks, 6 mg/day for 4 weeks) or prednisolone (11 mg/kg/day for 4 weeks, tapering for 8 weeks). Results. The groups were comparable for age, sex, pubertal stage, disease activity and disease duration. Mean morning plasma cortisol concentration was significantly higher in the budesonide group (200 nmol/1) than in the prednisolone group (98 nmol/1) after 8 weeks, reflecting less adrenal suppression by budesonide (difference -102 nmol/l; 95% Cl -226, -52; P = 0.0028). Glucocorticosteroid side effects such as moon face and acne occurred significantly less frequently in the budesonide group. Remission (Crohn's Disease Activity Index less than or equal to 150) was seen at 8 weeks in 12/22 (55%) patients treated with budesonide and in 17/24 (71%) patients receiving prednisolone (difference -16%; 95% Cl -45,13; P = 0.25). Conclusions Significantly fewer side effects and less adrenal suppression were observed in the children receiving budesonide. Remission rates were not significantly different in the two groups. However, there was a trend for prednisolone to be more effective for inducing remission. Eur J Gastroenterol Hepatol 16:47-54 (C) 2004 Lippincott Williams Wilkins.