Data obtained in a study of chemical composition of tissues in malnourished pre-school children are reported. In most cases, muscle and skin show an increase in total content of water, sodium and chloride. These changes are less striking but persist during "dehydration" judged on clinical grounds. The content of potassium in muscle was slightly to moderately decreased particularly in clinically edematous children. Edematous patients also had a markedly decreased intracellular concentration of potassium. In general, no correlation between intracellular concentration of sodium and potassium was found in muscle. Muscle obtained shortly before death or immediately after death frequently showed a marked shift of water and sodium into the intracellular compartment. A low ratio of concentration of potassium to noncollagenous nitrogen as compared to normals generally was observed. The skins of subjects without clinically demonstrable edema had comparable amounts of water but less fat per unit of dry fat-free solids than those of children with pitting edema. No particular correlation was found between overhydration and increase in content of the ("excess") chloride of the non-extracellular phase.