We studied the efficacy of cimetidine or placebo in relieving ulcer pain on 27 endoscopically-proven gastric ulcer outpatients in a randomized controlled prospective double blind trial. There were 12 patients in the cimetidine (1,200 mg daily) treated group and 15 patients in the placebo treated group. No antacid was allowed, but a placebo antacid with no neutralizing capacity was given as needed for pain. The incidence of complete pain relief at 2 and 4 weeks was 58% and 67% in the cimetidine treated patients, and 60% and 80% in the placebo treated patients. At 6 weeks of treatment there was no increase in the number of patients with complete pain relief in either group. There was no significant difference between the 2 groups in the incidence of ulcer pain relief at any of the 3 observation periods. Gastric ulcer healing rates and gastric ulcer pain relief were compared at 2 and 4 weeks. The cimetidine treated group healed 17% with 58% pain relief, and the placebo treated group had no ulcers healed at 2 weeks with 60% complete pain relief. There was no statistical association between ulcer healing and pain relief in both treatment groups at the 2 week evaluation period, but there was statistical association (P less than .05) at 4 weeks. The results of this study demonstrated that in gastric ulcer outpatients treated for 6 weeks: 1) the complete relief of gastric ulcer pain is not influenced by treatment with cimetidine when compared to placebo, and 2) there is no association between complete pain relief and the presence of an endoscopically proven gastric ulcer during the first 2 weeks of treatment with either cimetidine or placebo.