Rachel Yehuda, director of the Traumatic Stress Studies Program at the Bronx (N.Y.) VA Hospital, has compiled a useful series of articles summarizing what is and what is not known about risk factors associated with the development of posttraumatic stress disorder (PTSD). A potential challenge in any edited book is to avoid redundancy and promote cohesion; Dr. Yehuda has succeeded. She chose 8 distinct areas of focus for the contributing authors (for example, epidemiologic, genetic, familial, or psychophysiologic risk factors). With Phillip Harvey, her colleague at Mt. Sinai, she coauthored an introductory article that sets the tone for the rest of the volume, telling the history of trauma studies in the last 40 years, identifying important areas of inquiry, and cautioning readers about the limits of current data.