Traumatic experiences can lead to a range of mental health problems with posttraumatic stress disorder (PTSD) leading as the most documented disorder following trauma. Epidemiological research has found the rate of exposure to trauma to far outweigh the prevalence of PTSD. Indicating that most people do not develop PTSD following a traumatic event, this phenomenon has led to an interest in evaluating risk factors to determine who develops PTSD. Risk factors for the development of psychopathology following trauma exposure fall into three categories: pre-trauma, peri-trauma and post-trauma factors. Pre-trauma factors can include age, gender, race/ethnicity, education, prior psychopathology, and neurobiological factors. Peri-trauma factors can include the duration/severity of trauma experience and the perception that the trauma has ended. Post-trauma factors can include access to needed resources, social support, specific cognitive patterns, and physical activity. To date, several important risk factors have been found to impact the risk of developing PTSD including gender, age, education, IQ, race and ethnicity, sexual orientation, pre-trauma psychopathology, prior trauma exposure, familial psychiatric history, and neurobiological factors. This article outlines the state of research findings on pretraumatic, peritraumatic, and posttraumatic risk factors for the development of PTSD and associated psychopathology following trauma.