The duodenal pressure activity was studied by means of an intraluminal electrical transducer, and the recordings were compared to those of a traditional open-tip tube. The physiological significance of different pressure waves was studied by means of combined pressure and cineradiographic recordings. The recordings obtained by the intraluminal transducer were found to be essentially similar to those obtained by the open-tip tube. Most pressure waves observed in this study were found to cause a propulsive, mixed, or retropulsive movement of the intraluminal contents, and no significant displacement of the contents could be observed without simultaneous pressure waves. A difference in physiological significance of single and complex waves could not be detected. Rhythmic activity caused a rapid propulsion of intraluminal contents. It is concluded that the pressure recordings obtained by the intraluminal transducer are reliable in the study of duodenal motility.