In recent times it has come to be realized that pentoses are important as building blocks in the organism and as intermediate products in meta bolism. The finding that ribose and desoxyribose are nucleic acid con stituents and the discovery of the pentose-phosphate cycle have put these substances in a central position in biochemical research. The con current realization that the pentitol, xylitol, is involved in an important metabolic cycle and that the body can handle it in quantities comparable in magnitude to the well-known carbohydrates has resulted in extensive experimental and clinical...