There is little information about the organisation of antroduodenal contractions or pyloric motility in patients with gastroparesis. The mechanisms responsible for the acceleration of gastric emptying by cisapride in patients with gastroparesis are also poorly understood. Simultaneous manometric and scintigraphic recordings were performed in 12 patients with gastroparesis and nine healthy volunteers before and after cisapride administration. Antropyloroduodenal pressures were recorded with a sleeve/side hole manometric assembly and gastric emptying with a scintigraphic method. Thirty minutes after the solid component of the test meal had begun to empty from the stomach all subjects received 5 mg cisapride intravenously over 10 minutes and recordings continued for a further 60 minutes. In the 30 minutes before cisapride there was no significant difference in the number of antral pressure waves (median 20 v 33, NS), basal pyloric pressure, or the number of isolated pyloric pressure waves between patients and volunteers, but the number of antral waves of extent > or = 6 cm (median 1 v 5, p < 0.05) was less in the patients, as was gastric emptying (8% v 20%, p < 0.05). In the patients, there was no change in the number of antral waves after cisapride, but there was an increase in the number of antral waves > or = 6 cm in extent (median 7 v 1, p < 0.05) and in the rate of gastric emptying (26% v 8%, p < 0.01). In the healthy subjects, cisapride increased gastric emptying (31% v 20%, p < 0.05), but reduced the number of antral waves (10 v 33, p < 0.05). Cisapride had no significant effect on the number of antral waves of extent more than or equal to 6 cm (11 v 5, NS). The number of isolated pyloric pressure waves decreased after cisapride (4 v 11, p < 0.05). There was a relationship between gastric emptying and the number of antral pressure waves of extent more than or equal to 6 cm in both the patients (r=0.38, p<0.05) and healthy subjects (r=0.05, p<0.01). There was no significant relationship between gastric emptying and the number of antral waves. It is concluded that disturbance of the relationship between antral, pyloric, and duodenal pressure waves is a major abnormality of postprandial gastric motor function in patients with gastroparesis. The stimulation of antral pressure waves of extent more than or equal to 6 cm may contribute to the acceleration of gastric emptying produced by cisapride in patients with gastroparesis and in normal subjects.