This paper reports an observational study of the effects of handling on the social behavior of squirrel monkeys who received a protein deficient diet. After birth, experimental animals received a low-protein diet for a 6-week period. A subgroup of these animals were handled between 3 and 12 weeks of age. All of the animals interacted (in four animal social groups), five times a week beginning at 4 weeks of age. Animals were observed interacting twice-weekly. Results indicate that protein deficiency produces a general retardation of development as measured by locomotion, use of space and social contact. Between 20 and 41 weeks most of the differences had disappeared; the differences that did maintain offer evidence that handling attenuates the effect of protein deficiency, specifically in the area of motor behavior and activity. It is suggested that low levels of protein in the diet during the critical period of brain development cannot be compensated for fully by handling. Loss of the non-handled deprived group by death leaves unanswered the question of persistent effects of handling on the ultimate outcome of nutritionally deprived animals. (GO)