The effects of amphetamine on individual and social behaviors were studied in two colonies of rhesus monkeys. After an initial base-line period, each animal, in turn, received low chronic drug administration for 3 weeks. Between each drug period new base-line data were collected. During amphetamine administration, there was a significant increase in the following behaviors: time spent in "sit tense" postures, frequency of orienting, and frequency of agonistic behaviors. In addition, significant changes were seen in the time spent in proximity with other members of the group. The results are discussed both in terms of across-animal changes as well as with regard to social factors, rank in the hierarchy, and affiliative relationships.