In a double-blind randomized placebo controlled trial, 50 patients with endoscopically confirmed duodenal ulcer were treated with either misoprostol 200 micrograms or placebo in q.i.d. doses for 4-8 weeks. Of 25 patients in the placebo group, four defaulted and two were withdrawn due to worsening of symptoms. Of 25 misoprostol-treated cases, 17 cases (68%) and 21 cases (84%) healed at 4 and 8 weeks respectively, compared with three (14%) and five (24%) of the 21 placebo-treated cases (P less than 0.001). Except for diarrhoea in 2 patients in each group and itching in one with misoprostol, no serious side effects were noted.