The aim of the study was to investigate gastro-oesophageal function in normal subjects after oral administration of 150 mg ranitidine as a single dose. The study was designed as a double blind crossover investigation. Ten healthy men, aged 26-49 years (median 29 years) joined the study. A series of oesophageal function tests were performed, starting 90 minutes after oral intake of ranitidine or placebo. Gastro-oesophageal sphincter pressure was measured using a perfused catheter system and a continuous pull-through technique. No changes in sphincter pressure could be demonstrated. Peristaltic amplitude in the body of the oesophagus as well as the duration and velocity of the peristalsis were measured after wet swallows (bolus 5 ml of water). We found no changes in these variables. Intragastric pH was measured and was higher after ranitidine than after placebo (p less than 0.005). Plasma ranitidine concentration did not correlate with intragastric pH. No effect of ranitidine could be demonstrated on the results of a standard acid clearing test. It is concluded that ranitidine, given orally in sufficient doses to suppress gastric acid secretion, does not influence gastro-oesophageal sphincter pressure or peristaltic activity in the oesophagus of normal subjects.