As exposure to different types of traumatic stressors increases, the prevalence of PTSD increases. However, little is known about the effects of cumulative exposure to traumatic stress on the maintenance and remission from PTSD. In 2006/2007, we investigated 444 refugees from the 1994 Rwandan genocide, assessing exposure to traumatic events, current and lifetime PTSD, and PTSD symptom severity. Higher trauma exposure was associated with higher prevalence of current and lifetime PTSD, with lower probability of spontaneous remission from PTSD, and with higher current and lifetime PTSD symptom severity in clear dose-response effects. The results suggest traumatic load as a root cause of both PTSD chronicity and symptom severity and support the hypothesis of a neural fear network in the etiology of PTSD. (PsycINFO Database Record (c) 2016 APA, all rights reserved)