Thirty patients with symptoms of duodenal ulceration were treated for five to eight weeks in a double-blind trial with either metiamide 1 g daily by mouth or a placebo. In the 15 patients receiving metiamide there were significant reductions in nocturnal pain and antacid consumption. Daytime pain was diminished. The results suggest that histamine H2-receptor antagonists are likely to be useful in the medical management of the symptoms of duodenal ulceration.