Two directions of scientific research into primate cognition are leading to striking changes in our understanding of our relationship with primates. First, certain cognitive functions (memory, language skills, and social structures) are more advanced than previously thought. In some domains, such as immediate recall, chimpanzees are comparable -- or even superior -- to humans. Second, the range and severity of psychopathology in nonhuman primates are also greater than previously appreciated. Signs of depression, anxiety, and posttraumatic pathology are surprisingly common. This symposium presents recent breakthroughs in our understanding of primate cognition; describes new findings in primate psychopathology, creating a broader context for understanding human psychopathology; and provides a scientific basis for discussion of ethical considerations regarding the use of nonhuman primates in research. The Institute of Medicine recently issued new guidelines for the use of chimpanzees in research, which the National Institutes of Health are now implementing. This session focuses on the scientific underpinnings in this rapidly changing research landscape.