It is with great interest and concern for one of the major problems of our time, the chronic subalimentation affecting an impressive part of the world population, that we have met to discuss its disquieting consequences and its working solutions. Even though specialization within science has deepened our knowledge, facilitating comprehension of various aspects of malnutrition, it has not fully clarified the problem. The focus of this symposium is to explore the intertwining aspects of environmental and genetic factors as reflected in the physical and mental development of malnourished children. It is clear by now that geneticists do not always confirm the general observation of the clinician in the field of malnutrition. To start, the issue of optimal nutrition versus maximal nutrition raises a question as to the proper amount necessary for mental development. Obviously optimal and maximal physical and mental growth need to be clearly defined in terms of malnutrition before any valid conclusions can be drawn. In this respect another problem raised by the geneticist is the relationship between individual psychological and physiological variations as compared with group variations.