In the past two decades several new concepts have been developed with regard to the absorption, transit times, and colonic fermentation of common food carbohydrates. The progress in this research area is to a great extent due to the application of hydrogen (Hz) breath tests (1-4). Important dietary carbohydrates like starch and fructose (5-8) have been shown to be incompletely absorbed in the normal small bowel, serving as a substrate for the colonic bacterial flora. There is growing interest among physiologists and gastroenterologist in the consequences of ingestion of incompletely absorbed carbohydrates in humans, and fructose absorption has received much attention (9-11). However, several fundamental problems with regard to the intestinal handling of fructose and related carbohydrates are still unsolved. In the present review I shall present the state of art with regard to our knowledge of the basal mechanisms of fructose absorption and their possible implications in health and disease. Emphasis will be put on the experience from our breath H, studies of fructose, sorbitol, and fructans. Additional information on carbohydrate chemistry and physiology may be found in other reviews (12-14).