Patients with functional bowel disorders frequently complain of bloating and abdominal pain, but no practical method is available to measure intestinal gas objectively. To evaluate a new technique, we evaluated 54 abdominal radiographs from 19 patients. A gastroenterologist and a radiologist independently outlined the intestinal gas bubbles in these films. Areas of gas bubbles were measured with a computer digitizing board. Bowel gas was also measured in 24 healthy controls, and in five emergency room patients, supine and erect radiographs were compared to evaluate the effects of position on bowel gas patterns. The two evaluators agreed well on the measured areas of bowel gas (r = 0.96), showing that this is a reliable method. Bowel gas was significantly greater in patients than in controls but did not correlate with symptoms. Bowel gas was significantly greater in supine than upright films, showing that the position of the patient must be standardized.