Extracellular body fluid volume, as measured by the thiocyanate method, was found to increase per kilo of weight considerably in malnutrition. In severe malnutrition nearly half of the body is made up of extracellular water. The absolute amount of the latter is, however, decreased, though proportionately to a smaller extent than fat and protoplasmic tissue. The amount of cellular tissue is consequently even smaller than indicated by the proportion of the actual weight of the marantic infant to the ideal weight of healthy infants of the same age. The greater hydrolability of marantic infants is thought to have some bearing on the described change in the distribution of body fluids.