IN THIS MONOGRAPH we report the results of an experimental and ecologic study concerned with estimating some of the effects which malnutrition in early childhood may have upon neurointegrative functioning. In particular, we have been concerned with the association between malnutrition early in childhood and intersensory organization in children during the school years. A study of these relationships has derived from a concern with the possibility that inadequate food intake, particularly as represented by protein-calorie malnutrition, affects not only stature and weight, but also the capacity to learn. If this is indeed the case, then the significance of the observable and dramatic consequences of malnutrition for physical stature may be but one visible sign of functionally, perhaps, far more important non-visible handicapping. Findings on the effects which malnutrition has on the central nervous system suggest strongly that protein deficiency may result in structural lesions of the nervous system. Animals experimentally deprived are persistently delayed in achieving simple developmental landmarks, appear to be less adequate in environmental responsiveness and slower in learning as well as poorer in the retention of that which has been learned than normal controls. Considering the animal experiments and the findings in humans as a unit, one is led to be concerned with what in an ecologic sense could be called a "spiral" effect. A low level of adaptive capacity, ignorance, social custom, infection, or environmental paucity of foodstuffs appear to result in malnutrition which may produce a large pool of individuals who come to function in suboptimal ways.