The efficacy of cimetidine (1.6 g per day) was evaluated using a double blind placebo-controlled trial in 24 patients with moderate or severe peptic reflux esophagitis. The results show that cimetidine is superior to placebo when using endoscopic and histological criteria. Improved patient symptomatology and lower antacid comsumption failed to reach statistical significance. No change in the abnormally low lower esophageal sphincter pressure was observed at the end of the trial. No clinical side effects or significant biochemical changes were noted during the trial.