Various aspects of the primates' housing and rearing conditions, such as individual or sex differences, previous experience, husbandry, as well as the complexity of the animals' working and living environments, can have an impact on the specific design and success of an environmental enrichment program. Inherent characteristics of the subject are also known to influence behavior. For example, macaques of different age ranges will exhibit different behavioral profiles. Similarly, infant Chinese-derived and Indian-derived rhesus monkeys have different test scores on a Brazelton assessment. Forty-two rhesus monkeys, Macaca mulatta, of both sexes are being used for this study. Twenty-one animals were randomly chosen from the NIA calorie-restricted groups and twenty- one additional animals were chosen from the NIA control groups. An A-B-A paradigm is being used to evaluate the effect(s) of age (and secondarily caloric intake, sex and subspecies) on the behavior profile of the subjects. Preliminary data indicate that there are differences in the behavioral profiles of calorie-restricted and control primates on a long- term aging study. Additional data are being collected for analysis.