Due to their genetic, behavioral, and physiological similarities to humans, rhesus macaques (Macacca mulatta) have long been used as a translational model in biomedical research. However, studies using very old monkeys have been impeded by lack of access to animals of advanced age. As the average lifespan of a rhesus macaque is reported to be 25 years, acquiring animals of this age can be both time- and cost-prohibitive. Our laboratory, via a collaborative pooling of resources, has access to postmortem tissue from a cohort containing some of the oldest known macaques in the world, with three animals having lived more than 40 years. Due to this unique resource, we are able to examine whether specific normative or pathological brain aging processes occur in the macaque brain. Specifically, we are interested in whether the rhesus monkey naturally develops Alzheimer's disease (AD) phenotypes.