This paper outlines research designed to establish dietary correlates of malnutrition, and questions the common assumption that high protein foods should be used as dietary supplements in humans. Because thorough investigation of dietary needs in children is ethically unfeasible, squirrel monkeys were used in the research to study the biological and mental effects and the behavioral correlates of deficiency disease. Infant squirrel monkeys were taken from their mothers after birth and fed a low-protein diet from 2 weeks to 8 weeks of age. Group rearing conditions were provided by satellite cage arrangements for every four animals. The members of these social groups were allowed to interact for four hours a day. All animals were given normal diets at the age of 8 weeks. (GO)