James, W. P. T. (1972). Archives of Disease in Childhood, 47, 531. Comparison of three methods used in assessment of carbohydrate absorption in malnourished children. The results of oral lactose and sucrose tolerance tests were compared with jejunal disaccharidase activities and the absorption rates of lactose and sucrose from a perfused segment of jejunum in 8 malnourished children before and after treatment.Treated children, with nearly normal utilization of circulating glucose, showed a good correlation between the oral tolerance test results and the jejunal absorption rates of lactose and sucrose. Malnourished children often showed normal rises in blood glucose despite low disaccharidase activities and poor jejunal absorption rates of glucose, lactose, and sucrose. These rises were considered to reflect poor glucose uptake by peripheral tissues rather than adequate absorption of sugars from the distal small intestine.Jejunal absorption of lactose and sucrose was only limited by the disaccharidase activities when these were very low; the rate of disaccharide absorption was usually closely related to the rate of glucose absorption, despite a wide range in disaccharidase activities.Several tests have been used in children and adults in an attempt to establish whether patients are able to hydrolyse and absorb the different forms of carbohydrate in the diet.The 3 clinical methods at present available are the oral tolerance test, the direct measurement on jejunal mucosa of carbohydrase activities, and observations on the faecal pH and output of water and sugar. Other methods, including hydrogen excretion measurements of the breath, and intubation studies of the small intestine for sampling after feeds or perfusion of the jejunum, are at present used only as research tools.Diarrhoea is a more prominent feature of carbohydrate intolerance in children than in adults.This difference presumably reflects the importance of the adult colon in reducing the loss of water (Dawson, 1970). Colonic bacterial fermentation, with the production of organic anions from unabsorbed sugar, will also affect the amount of carbohydrate and water in the stool, and this fermentation process may differ in children and adults. In children the severity of the diarrhoea and measure-