Each year behavioral problems stemming from fear, nervousness or aggression result in dogs being surrendered to animal shelters or euthanized. Unfortunately, these problematic behaviros are often not recognized until the dog is adopted into a home, bred, or placed in a working role. For assistance dog organizations, temperament problems account for nearly 70 percent of the dog failure rate. Our project begins with the finding that an important component of temperament is rooted in emotional reactivity. Our multi-stage project seeks to define both an objectively scored behavioral test and a physiological parameter, the dog’s fecal cortisol profile (FCP), that can be used to describe and quantify canine emotional reactivity. Unlike other physiological indicators of stress, assaying the FCP is non-invasive and reflects adrenal activity over time. The FCP should therefore be less sensitive to episodic and circadian fluctuations in adrenal secretions and allow us a clearer picture of whether an animal is chronically hypersecreting due to a higher degree of emotional reactivity. The project makes use of the large canine population at Canine Companions for Independence, which ranges in age from newborns to seniors and includes purebred Labrador and Golden Retrievers.