Animal models of stress have the potential to provide information about the course and etiology of posttraumatic stress disorder (PTSD). To date, however, there have been no systematic approaches for evaluating the relevance of animal models of stress to PTSD. It has been established in the animal literature that different types of stress paradigms lead to different biobehavioral consequences and that many different factors contribute to differential responsivity to stress. It becomes important therefore to differentiate between factors that are essential to the induction of PTSD-like symptoms and those that influence their manifestations. In the present commentary, we present five criteria that must be fulfilled by animal models of stress for them to be useful to understanding the induction of PTSD. We then evaluate two potential animal models of stress--inescapable shock-learned helplessness and time-dependent sensitization--to illustrate how to more successfully pair animal models of stress with the specific clinical syndrome of PTSD.