BACKGROUND: It is unknown if abdominal bloating is attributable to excess abdominal gas or improved by a prokinetic agent. AIMS: To assess abdominal gas content in functional abdominal bloating and to ascertain the effect of a prokinetic agent on intestinal gas symptoms in these patients. METHODS: In 20 patients, intra-abdominal gas content and symptoms were quantified before and during treatment with pyridostigmine (30 mg/8 hp. o) in this randomized, placebo-controlled, double-blind study. Daily symptoms were quantified for 5 days before and 10 days during treatment, and abdominal gas volume was quantified by CT imaging before and at the fourth day of treatment. A CT scan was also obtained in 10 healthy subjects. RESULTS: Before treatment, the total volume of intestinal gas was similar in patients (112 ± 18 mL) and in healthy controls (116 ± 20 mL). The treatment-induced change in total and regional intestinal gas volume was not significantly different between pyridostigmine (-4 ± 18 mL; mean ± SEM) and placebo (0 ± 15 mL). However, pyridostigmine reduced the severity of bloating from 3.3 ± 0.3 to 2.6 ± 0.4 (P < 0.05), whereas placebo did not (3.2 ± 0.3 vs 3.0 ± 0.4), although the change did not reach statistical difference across groups. CONCLUSION: In patients complaining of functional bloating, the volume and distribution of intestinal gas, measured on nonselected days, is comparable to asymptomatic subjects. Prokinetic stimulation improves bloating sensation without detectable changes in gas content. © 2008 by Am. Coll. of Gastroenterology.