Pavlovian conditioning paradigms have become important model systems for understanding the neuroscience of behavior. In particular, studies of the extinction of Pavlovian fear responses are yielding important information about the neural substrates of anxiety disorders, such as phobias and post-traumatic stress disorder (PTSD) in humans. These studies are germane to understanding the neural mechanisms underlying behavioral interventions that suppress fear, including exposure therapy in anxiety disorders. This unit describes detailed behavioral protocols for examining the nature and properties of fear extinction in laboratory rodents.