Cisapride is a prokinetic agent believed to facilitate acetylcholine release from the myenteric plexus of the gut. The effect of cisapride on gastric emptying of solids was studied in 9 diabetic patients, all of whom had delayed gastric emptying of indigestible solids (gastroparesis). Six patients had chronic nausea and vomiting, and 3 had no symptoms. Cisapride (5 mg) was given intravenously 15 min before ingestion of a 400-kcal test meal and 10 indigestible solid radiopaque markers. On separate days and in random order each patient also received intravenous metoclopramide (10 mg) or placebo 15 min before ingestion of the meal and markers. Mean gastric emptying of radiopaque markers, assessed by serial radiographs of the gastric region, was accelerated by metoclopramide and cisapride, but the difference reached significance only with cisapride (p less than 0.05). There was considerable intersubject variability in gastric emptying responses to cisapride and metoclopramide. No side effects occurred with either drug. This study indicates that acute, intravenous administration of cisapride accelerates gastric emptying of indigestible solids in patients with diabetic gastroparesis.