First published in 2001. This is Volume 10 of ten of a series on the science of Mental Health. Originally published in 2001, this study looks at fear and anxiety. During the past decade there has been substantial progress in the understanding of one emotion in particular: fear. There are descriptions of some of the clinical syndromes followed by sections on epidemiology, genetic and environmental risk factors, and natural history (course of illness). Because anxiety disorders so often co-occur with other mental disorders, there is a section devoted to this issue. The volume also includes an article on the evolutionary psychology of anxiety disorders and a long section on brain and behavior that, among other issues, illustrates current attempts to use new insights into fear circuitry in the brain to help investigate the pathogenesis of anxiety disorders. The volume ends with a section on treatment. In some sections there are articles on panic disorder, PTSD, GAD, social anxiety disorder, and, where appropriate, childhood anxiety disorders (which are not always readily separated into their adult forms). Because simple phobias cause relatively little harm or impairment compared with the other anxiety disorders, they are little discussed.