A study of the motor activity of the gastroduodenal (GD) junction has been carried out on 8 subjects by using an original probe provided with a suction cup, that allows not only a duodenogastric (DG) pull-through, but also a prolonged recording of the pyloric, antral and duodenal motor activity, in basal condition and after intraduodenal instillation of HCl 0.1 N and intravenous infusion of cerulein. The position of the probe was controlled with fluoroscopy and transmural potential difference. The DG pull-through did not show a zone of high pressure at the GD junction, but the prolonged study showed, during HCl and cerulein administrations, a significant increase of the pyloric tonus.