Gastric acid secretion, gastric emptying of solids, and the effects of short-term treatment with 300 mg ranitidine at bedtime were evaluated in symptomatic patients with endoscopically and histologically proven duodenitis. The patients investigated had basal and pentagastrin-stimulated gastric acid hypersecretion, but normal gastric emptying times. Ranitidine brought about a significant improvement of endoscopic and histological features compared with the pretreatment findings. Endoscopic but not histological improvement was significantly better than with placebo. Furthermore, ranitidine brought about a significant reduction of weekly antacid consumption compared with placebo. Both ranitidine and placebo induced significant symptomatic improvement over basal conditions, but the difference between the two treatments did not reach statistical significance. Gastric secretory and motor functions, as well as the response to therapy, were similar in duodenitis patients with and without previous history of duodenal ulcer; the only exception was in antacid consumption, which was higher in the placebo group in those with past evidence of ulcer disease. Our results suggest that duodenitis patients have secretory and motor functions similar to those of duodenal ulcer patients. Therefore, further trials on large populations of duodenitis patients with antisecretory drugs are justified.