Oat extract has been shown to modify blood glucose response and fasting lipids after dietary incorporation although some abdominal discomfort and increased flatulence were noted. To determine the extent of gas production, hydrogen and methane were determined after tolerance tests containing cooked and uncooked oat extract and after dietary incorporation. Breath gases were determined before and periodically after tolerance tests. Study 1: While consuming a maintenance diet, 24 subjects (55.3-112.5 kg body weight) underwent a tolerance test (1 g carbohydrate/kg body wt) of glucose (GTT, 1700 kJ/100 g) or uncooked, baked, or boiled pudding [2191 kJ/100 g carbohydrate, (0.67 glucose and 0.33 oat extract containing 10 g/100 g beta-glucan)]. Hydrogen and methane expiration after all tolerance tests with the oat extract puddings, regardless of cooking method, was significantly higher than expirations after the GTT. Cooking the oat extract did not significantly change hydrogen or methane expiration. Study 2: Twenty-three subjects consumed a maintenance diet followed by the incorporation of oat extracts (50 g/8.33 MJ, 1 or 10 g/100 g beta-glucan) to the diet in a crossover pattern. A GTT and a tolerance test containing 0.67 g glucose and 0.33 g of the respective oat extract/kg body weight were consumed after the maintenance and oat extract diet periods. Breath hydrogen was significantly higher after both oat extract tolerance tests than after the GTT. Hydrogen excretion after the 10% beta-glucan oat extract was higher at 4, 5 and 6 h than after the 1% beta-glucan oat extract; breath methane was not significantly different. These data indicate that cooking did not alter the influence of oat extracts on intestinal function, and increased beta-glucan marginally increased hydrogen expiration.