A washout technic with intestinal infusion of an inert gas mixture was used to study the relation of gas to functional abdominal symptoms. The volume of gas in the intestinal tract (176 plus or minus 28 ml S.E.M.) of 12 fasting patients with chronic complaints of excess gas did not differ significantly (P greater than 0.10) from that of 10 controls (199 plus or minus 31 ml). Similarly, there was no difference in the composition or accumulation rate of intestinal gas. However, more gas tended to reflux back into the stomach in patients who complained of abdominal pain during infusion of volumes of gas well tolerated by controls. Six patients with severe pain during the study had intestinal transit times of gas (40 plus or minus 6 minutes S.E.M.) that were significantly (P less than 0.05) longer than those of the control group (22 plus or minus 3 minutes). Thus, complaints of bloating, pain and gas may result from disordered intestinal motility in combination with an abnormal pain response to gut distention rather than from increased volumes of gas.