BackgroundA fast-growing population of refugees and survivors of violent conflict and atrocities are at risk for trauma-related mental health problems. Experimental clinical research key to the development of interventions tailored to this population is limited. AimsIn an experimental psychopathology laboratory paradigm, we tested the expression and function of avoidance in posttraumatic stress (PTS) among a highly traumatized community sample of forcibly displaced refugees seeking asylum. MethodWe measured behavioral avoidance and emotional reactivity to repeated exposure to threatening stimuli (trauma-, war-, and geographically-relevant natural threat) in 110 Sudanese male asylum seekers (M(SD)age = 32.7(6.5)) recruited from the community in Israel. ResultsFirst, we found evidence of sensitization – traumatized refugees expressed increasing levels of behavioral avoidance and emotional reactivity in response to repeated exposure to threatening stimuli. Second, as predicted, refugees suffering from more severe PTS were more likely to exhibit greater behavioral avoidance and emotional reactivity reflexively or immediately upon exposure to threat stimuli. Finally, as predicted, behavioral avoidance mediated the effect of PTS severity on emotional reactivity to threat exposure. ConclusionsFindings are consistent with theorizing that avoidance may function as a trans-cultural malleable risk process sub-serving PTS and thereby a promising intervention target among highly traumatized refugees from E. Africa.