Twenty patients with symptoms and endoscopic changes of gastro-oesophageal reflux were randomly allocated to treatment with either ranitidine 150 mg bd, or 300 mg bd for 8 weeks. Symptoms, endoscopic appearances, histopathology of oesophageal biopsies and 22-h intra-oesophageal pH profile in ambulant patients on standard diets were recorded before and at the end of the treatment period. Symptoms improved rapidly and markedly on either dose of ranitidine. Both doses produced significant improvement of the endoscopic appearances, but there were no differences in symptomatic and endoscopic improvement related to the dose. Biopsy appearances and the 22-h oesophageal pH profile remained unchanged on either dose of ranitidine.