Ninety patients with endoscopically proven duodenal ulcers, enrolled in this prospective, single-blind study, were randomized to sucralfate, 1 g q.i.d., 0.5 hour before meals on an empty stomach or at bedtime, or ranitidine, 150 mg b.i.d., for 4-8 weeks (phase I). Patients who healed during the treatment period were invited to participate in a maintenance therapy follow-up covering 1 year (phase II), during which they were treated with sucralfate, 1 g b.i.d. (before breakfast and at bedtime) or 150 mg of ranitidine at bedtime. After 4 weeks of treatment, healing rates were 30 40 (75.0%) with sucralfate and 36 42 (85.7%) with ranitidine, and healing rates were 39 40 (97.6%) and 40 42 (95.2%) respectively, after 8 weeks of treatment. At the end of the 6th and 12th months of phase II, respectively, relapse rates were 3 33 (9.4%) and 10 32 (31.3%) in the sucralfate group and 5 33 (15.2%) and 10 29 (34.5%) in the ranitidine group. Differences between sucralfate- and ranitidine-treated groups were not significant. Both treatments were well tolerated. We conclude that sucralfate is as effective and safe as ranitidine in the short-term treatment and prevention of relapse in patients with ulcer disease. © 1991.