Upper gastrointestinal motor function and incretin hormone secretion are major determinants of postprandial glycemia and insulinemia. However, the impact of small intestinal flow events on glucose absorption and incretin release is poorly defined. Intraluminal impedance monitoring is a novel technique that allows flow events to be quantified. Eight healthy volunteers were studied twice, in random order. A catheter incorporating 6 pairs of electrodes at 3 cm intervals, and 6 corresponding manometry sideholes, was positioned in the duodenum. Hyoscine butylbromide 20 mg, or saline, was given as an intravenous bolus, followed by a continuous intravenous infusion of either hyoscine (20 mg/h) or saline, over 60 minutes. Concurrently, glucose and 3-O-methylglucose (3-OMG) were infused into the proximal duodenum (3 kcal/min), with frequent blood sampling to measure glucose, 3-OMG, insulin, glucagon-like peptide-1 (GLP-1) and glucose-dependant insulinotropic polypeptide (GIP). The frequency of duodenal pressure waves and propagated pressure wave sequences was reduced by hyoscine in the first 10 minutes (P<0.01 for both), but not after that time. In contrast, there were markedly fewer duodenal flow events throughout 60 minutes with hyoscine (P<0.005). Overall, blood glucose (P<0.01) and plasma 3-OMG concentrations (P<0.05) were lower during hyoscine than saline, while plasma insulin, GLP-1, and GIP concentrations were initially (t=20 min) lower during hyoscine (P<0.05). In conclusion, intraluminal impedance measurement may be more sensitive than manometry in demonstrating alterations in duodenal motor function. A reduction in the frequency of duodenal flow events is associated with a decreased rate of glucose absorption and incretin release in healthy subjects.