Ranitidine (150 mg X 2) and placebo were given to 42 patients with reflux oesophagitis for 8 weeks by the double-blind crossover technique. Gastric secretion tests and 24-h pH monitoring at two different oesophageal levels were performed before and during the treatment periods. Gastric hypersecretion was present in 76%. Ninety-seven per cent had reflux for more than 1% of 24 h, and 67% for more than 4.2%. Ranitidine reduced basal and stimulated gastric acid output and secretion rates (p less than 0.001), total reflux time to the lower level (p less than 0.05), and number of reflux episodes to the upper and lower levels of the oesophagus in the supine position. Basal, maximal, and peak acid output, gastric secretion rates, number of reflux episodes, and total reflux time at the upper oesophageal level in the supine position were significantly more reduced in symptomatic responders than in non-responders. No correlation was found between ranitidine-induced reduction of gastric secretion and length of oesophageal reflux time.