Of all the animals used for invasive research, nonhuman primates are perhaps the most controversial. While the total number of animals used in experiments and covered by animal welfare laws has declined in recent years, the number of nonhuman primates used has increased. Those primates include macaques, baboons, monkeys, and chimpanzees. HIV studies account for most of the research involving nonhuman primates, followed by neurological research, and developmental research.
Source: USDA