Available data on the efficacy of activated charcoal in reducing lower intestinal gas and accompanying symptoms are conflicting. We conducted a double-blind clinical trial on two population groups in the United States (n = 30) and India (n = 69) known to differ in their dietary habits and ecology of gut flora. Using lactulose as the substrate, breath hydrogen levels were measured to quantify the amount of gas produced in the colon. In comparison to a placebo, activated charcoal significantly (p less than 0.05) reduced breath hydrogen levels in both the population groups. Symptoms of bloating and abdominal cramps attributable to gaseousness were also significantly reduced in both groups by activated charcoal.