BACKGROUND AND AIMS: Patients frequently complain of gas symptoms precipitated by meals, but the effect of early digestion on intestinal gas content remains unknown. Our aim was to determine the influence of meals on intestinal gas volume and distribution. METHODS: First, we developed a CT image analysis program, based on independent software modules, to measure gas content within the gut. The system was validated in nine healthy subjects by taking helical abdominal CT scans before and after rectal infusion of known volumes of air (100-400 mL). In 15 healthy subjects, intestinal gas distribution was measured in fast and early postcibal CT scans. The postcibal scan was taken 99 ± 22 minutes after a 597 ± 57 kcal meal. RESULTS: The volume of gas infused per rectum was detected with an accuracy of 100.4 ± 3.0%. During fasting, intestinal gas volume was 94 ± 7 mL (excluding two extreme outliers). After the meal, gas content within the gut increased by 64.7% (up to 149 ± 21 mL, P < 0.01 vs fast) and the increment occurred in the colon (59 ± 9 mL precibal vs 121 ± 20 mL postcibal, P < 0.001), while other gut compartments remained unchanged. CONCLUSION: Ingestion of a meal activated gas metabolism and increased gas content within the gut. The increment occurred early, presumably prior to colonic fermentation of food substrates and was localized in the distal gut, suggesting that gas had a proximal origin and was propelled caudally. © 2007 by Am. Coll. of Gastroenterology.