The efficacy and safety of omeprazole, 40 mg once daily for four to eight weeks of treatment, were studied in 61 patients with ulcerative reflux esophagitis. A double-blind controlled study design was used, and the patients were randomly allocated to treatment with either omeprazole 40 mg once daily or ranitidine 150 mg twice daily. Endoscopy was performed prior to inclusion into the study, after four weeks and, if unhealed, again after eight weeks. Healing of esophagitis was defined as complete disappearance of all esophageal ulcerations. Symptoms were recorded before entry, after four weeks, and again after eight weeks in unhealed patients. Fifty-one patients were included in the per-protocol analysis at day 29, and 50 patients at day 57. The healing rate after four weeks of treatment was 22 of 26 patients (85%) treated with omeprazole and 10 of 25 patients (40%) treated with ranitidine (P less than 0.001). The corresponding figures after eight weeks were 24 of 25 (96%), and 13 of 25 (52%) (P less than 0.001). These results were confirmed in the intent-to-treat analysis. Patients treated with omeprazole showed a significantly faster and more profound relief in heartburn than patients treated with ranitidine: 85% had no heartburn after four weeks of treatment with omeprazole compared to 24% in patients treated with ranitidine (P = 0.00007). The percentage of patients who were free of all reflux symptoms was significantly greater in the omeprazole-treated group as compared to the ranitidine-treated group (62% and 12% respectively; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)