Some patients with gastro-oesophageal reflux disease have delayed gastric emptying. This study investigates the effect of cisapride on gastric emptying in 34 patients with proved reflux and delayed gastric emptying of solids. They were enrolled in a double blind controlled crossover study. Placebo or cisapride (10 mg) tablets were given three times a day for three days followed by further assessment of gastric emptying. The protocol was repeated with the crossover tablet. Gastric emptying was assessed by a dual radionuclide technique. The percentage of a solid meal remaining in the stomach at 100 minutes (% R100 minutes) and the time taken for 50% of the liquid to empty (T50 minutes) were calculated and analysed by the Wilcoxon matched pairs signed ranks test and expressed as medians (ranges). For gastric emptying of solids the initial % R100 minutes (70 (60-100)%) was not significantly different from placebo (71 (35-100)%). After cisapride treatment a significant acceleration (p less than 0.001) in gastric emptying occurred (% R100 minutes, 50.5 (28-93)%). Similarly with gastric emptying of liquids, the initial T50 minute value was 26.5 (12-82) minutes, after placebo the value was 28 (11-81) minutes, but this was significantly accelerated with cisapride (p less than 0.03) to 22.5 (6-61) minutes. The acceleration in gastric emptying occurred in the proximal portion of the stomach for gastric emptying of both solids and liquids suggesting that this is the principal site of action of cisapride. We conclude that cisapride significantly accelerates gastric emptying of both solids and liquids in patients with gastro-oesophageal reflux disease and delayed gastric emptying.