Background: Patients describe that body posture may affect their abdominal bloating, distension, and flatulence, but whether changes in position have objectively demonstrable effects, either beneficial or deleterious, has not been investigated. Aim: To determine the effect of body posture, upright versus supine, on intestinal transit of gas loads. Subjects: Eight healthy subjects without gastrointestinal symptoms. Methods: In each subject a gas mixture was continuously infused into the jejunum (12 ml/min) for three hours, and gas evacuation, clearance of a non- absorbable gaseous marker, perception, and abdominal girth were measured. Paired studies were randomly performed in each subject on separate days in the upright and supine positions. Results: In the upright position, intestinal gas retention was much smaller than when supine (13 (52) ml v 146 (75) ml retention at 60 minutes, respectively; p<0.05), and clearance of the gas marker was expedited (72 (10)% clearance v 49 (16)% at 60 minutes, respectively; p<0.05). The gas challenge test was well tolerated both in the upright and supine positions without abdominal distension. Conclusion: Body posture has a significant influence on intestinal gas propulsion: transit is faster in the upright position than when supine.