A preliminary, double-blind placebo controlled trial of cisapride in reflux oesophagitis was conducted. Eighteen patients were allocated to treatment with either placebo or cisapride, 10 mg three times daily, orally, before meals. Gastric emptying of a scrambled egg meal, oesophageal transit of a liquid bolus and ambulatory monitoring of oesophageal pH were assessed before and after four weeks' therapy. Overall, gastric emptying rates were not influenced by cisapride, although a small but significant reduction in gastric isotope retention, 20 minutes after meal ingestion was observed in patients on the active drug. Oesophageal transit times were not altered by cisapride. A small but significant reduction in the duration of gastro-oesophageal reflux followed cisapride therapy when compared with placebo.