We undertook a multicenter double-blind study comparing ranitidine to placebo in 73 patients with symptomatic gastroesophageal reflux ranging in age from 22 to 80 years (mean 49). Initially, all patients had moderate to severe symptoms associated with abnormal endoscopic and/or microscopic appearance of the mucosa. After six weeks, 46% of ranitidine-treated patients had a one-grade improvement in their symptom of regurgitation, as compared with 19% treated with placebo (p less than 0.01); ranitidine was no better than placebo in the improvement of pain or dysphagia. Endoscopic improvement occurred in 61% of ranitidine- and 48% of placebo-treated patients (p less than 0.05). Histological improvement occurred in a similar and small portion of patients treated with ranitidine and placebo; there was no correlation between clinical, endoscopic, and histological improvement. Antacid consumption was only half as great in the ranitidine as in the placebo group. Therapy with ranitidine was maintained for up to 12 months. The patients remained free of regurgitation or pain and there was a trend towards further improvement in the endoscopic or histopathologic appearance of the esophagus. Ranitidine 150 mg b.i.d. is recommended for the relief of symptoms and improvement in the endoscopic appearance of the esophagus. Treatment should be for a minimum of 6 weeks, but may be continued for up to a year if the patient's symptoms persist or return.