A multicenter study was carried out in India to determine the incidence of lactose intolerance in healthy volunteers from different parts of the country. The incidence was found to be 66.6% in the subjects from two South Indian centers at Trivandrum and Pondicherry. In contrast, the incidence in the subjects from a North Indian center in New Delhi was much lower, i.e., 27.4% (p less than 0.001). The lower incidence in the North Indian subjects may perhaps be due to the fact that they are descendants of the Aryans who have been dairying for long and are known to be lactose tolerant.