Therapy of acute intestinal GVHD is still one of the main challenges after allogeneic transplantation. Increasing systemic immunosuppression (IS) is the first choice and includes corticosteroids and lymphocyte antibodies, often associated with severe side-effects. In inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, topical steroid therapy is used very successfully. Because of the similarity between these and acute intestinal GVHD we conducted a trial with oral budesonide (Budenofalk), a new topically active glucocorticoid, to treat patients with acute GVHD > or = grade II. After a diagnosis of aGVHD > or = grade II, 22 patients received increased IS, mainly systemic corticosteroids, and additionally budesonide 9 mg/day divided into three doses. Improvement in aGVHD, infectious side-effects, reduction of systemic IS and outcome were documented. Results were compared with the results of 19 control patients, who were treated only by increasing IS dose. In 17/22 patients (70%), treated with budesonide, the acute intestinal GVHD resolved and no relapse occurred after decreasing the systemic IS, while continuing budesonide. In only 8/19 patients in the control group did the acute intestinal GVHD resolve and 2/8 patients had a relapse of intestinal GVHD after decreasing IS, with an overall response of 33%. No severe intestinal infections occurred. We conclude that budesonide may be effective in acute intestinal GVHD as a topical corticosteroid and prospective, randomized studies should demonstrate its efficacy in allowing reduction of systemic immunosuppressive therapy, and its side-effects.