This multicenter trial investigated the ability of the cytoprotective agent sucralfate and the antisecretory agent cimetidine to prevent ulcer relapses. Seventy-one patients with recently healed duodenal ulcer were included, randomly assigned to one of the two treatment groups, and administered sucralfate 2 g per day or cimetidine 400 mg per day for six months; the treatment period was followed by another six months of follow-up without treatment. The response to therapy was evaluated by systematic single-blind endoscopy controls during the sixth and the 12th months. Quantitative (42 percent relapse rate with sucralfate and 52 percent with cimetidine) as well as qualitative (20 percent silent relapses with sucralfate and 47 percent with cimetidine) differences were observed, although these could not be demonstrated to be statistically significant.