During the past ten years, from our studies of deficiency diseases in human beings, we have accumulated evidence which shows that pellagra, beriberi and riboflavin deficiency are clearcut clinical syndromes which frequently coexist and often are associated with other nutritional disorders. This is not surprising, since in natural foodstuffs the water-soluble vitamins are often closely associated and a diet deficient in one chemical substance is almost certain to be deficient in others. In the nutrition clinic at the Hillman Hospital we find that the unbalanced and inadequate diets eaten by the majority of the patients predispose them simultaneously to a number of nutritional disorders and that the diagnosis of one clinical deficiency syndrome necessitates a thorough search for others. There are thirty-six known constituents of the diet which are essential for adequate nutrition, and it is likely that there are others as yet unknown. Very little significant information has been