Comparison of omeprazole and cimetidine in reflux oesophagitis: symptomatic, endoscopic, and histological evaluations. Symptomatic patients with endoscopically verified reflux oesophagitis were randomised to a double blind trial in which they received either omeprazole (20 mg once daily) or cimetidine (400 mg four times daily) for four, and if necessary, eight weeks. In an 'intention to treat' analysis, oesophagitis was found to have healed after four weeks in 77 of 137 (56%) in the omeprazole group and in 34 of 133 (26%) in the cimetidine group (p less than 0.001). By eight weeks these values were 71% and 35% respectively; p less than 0.001. Histological assessments were available for 73% of the patients. At entry, 63% (66 of 104) in the omeprazole group and 60% (56 of 94) in the cimetidine group (ns) had abnormal histology. After the study, the proportions of patients who initially had had abnormal histology but who then progressed to normal were 67% (44 of 66: omeprazole) and 48% (27 of 56: cimetidine) respectively (p less than 0.001). All patients had reflux symptoms at entry. After four weeks, 46% in the omeprazole group and 22% (p less than 0.001) in the cimetidine group were asymptomatic. Diary cards completed for the first two weeks showed that patients treated with omeprazole experienced fewer reflux symptoms by day and night and used fewer antacids. Omeprazole, 20 mg once a day for four to eight weeks, healed a greater proportion of patients with reflux oesophagitis than cimetidine, 1.6 g per day, assessed endoscopically and histologically, and relieved more patients' symptoms. 