Progress in gerontological research has been promoted through the use of numerous animal models, which have helped identify possible mechanisms of aging and age-related chronic diseases and evaluate possible interventions with potential relevance to human aging and disease. Further development of nonhuman primate models, particularly rhesus monkeys, could accelerate this progress, because their closer genetic relationship to humans produces a highly similar aging phenotype. Because the relatively long lives of primates increase the administrative and economic demands on research involving them, new emphasis has emerged on increasing the efficient use of these valuable resources through cooperative, interdisciplinary research.