Social behavior of rhesus macaques placed on repletion diets after periods of up to 3 yr of chronic protein malnutrition was measured in a playroom situation. Observations of experimental and control groups were made 5 days a week for 5 wk prior to and beginning again 30 days after the initiation of repletion. The behaviors observed prior to nutritional rehabilitation were similar to that reported in previous experiments. Nutritionally deprived animals showed higher rates of aggression, less play behavior, less tactual contact, and a greater amount of nonsocial behavior. The animals undergoing nutritional rehabilitation showed significant increases in frequency and duration of approach-play, significant reductions in nonsocial behaviors, and rates of aggression. Although the behavior patterns still did not reach control levels, the changes in the previously malnourished monkeys apparently made these animals more adaptive in the social situations. It was suggested that there were two phases or aspects of recovery. First, behavior patterns which appear after social contact is made recover as a result of nutritional repletion and second, behavior patterns that are necessary for the frequent initiation of social contact may require longer periods of positive social experience.