Twenty-three patients with attacks of distal ulcerative colitis were treated randomly with either 2 or 3 mg of topically administered beclomethasone dipropionate (BDP) or 30 mg of prednisolone sodium phosphate (PP). The effect of the steroid enemas on adrenocortical function was assessed by ACTH tests, which were performed before and after treatment. Endoscopic, clinical and histological scores were comparable in the three treatment groups in this pilot trial. Fasting cortisol in the PP group decreased significantly from 0.47 +/- 0.12 mumol/l before to 0.22 +/- 0.14 mumol/l (P less than 0.05) after therapy; in the BDP group no significant changes were found. Urinary cortisol excretion in the PP group was not detectable after therapy; in the BDP group no changes were found. It is concluded that in the topical treatment of ulcerative colitis, BDP may be preferable to PP because it exerts a promising anti-inflammatory action without affecting adrenocortical function.