Posttraumatic stress disorder (PTSD) has a discernible starting point and typical course, hence the particular appropriateness of longitudinal research in this disorder. This review outlines the salient findings of longitudinal studies published between 1988 and 2004. Studies have evaluated risk factors and risk indicators of PTSD, the disorder's trajectory, comorbid disorders and the predictive role of acute stress disorder. More recent studies used advanced data analytic methods to explore the sequence of causation that leads to chronic PTSD. Advantages and limitations of longitudinal methods are discussed.