Gastrointestinal (GI) distension by gas expansion may be more of a problem in diving than is usually recognized. In response to a written questionnaire, 2053 scuba divers gave information about GI discomfort such as pain, nausea, and vomiting in connection with diving. One hundred and eleven reports (5.4% of 2053) were considered possible cases of significant GI distension because the majority of divers had their symptoms during ascent and a significant number of them got relief from belching. Difficult middle ear pressure equilibration was a particular problem among divers with GI symptoms. It may have induced frequent swallowing, causing air ingestion and consequent GI problems. Steep, head-first descents appear to have been employed in some dives, leading to GI discomfort presumably be creating large mouth-to-stomach gas-pressure differences. It was concluded that swallowing or any procedure leading to entry of gas into the stomach should be avoided and that belching during diving should be recommended.