Cognitive bias was investigated in survivors of motor vehicle accidents with either acute stress disorder (ASD; n = 17) or no ASD (n = 17). Participants completed the acute stress disorder interview, the Beck depression inventory, the Beck anxiety inventory, the impact of event scale, and a probability questionnaire (PQ) and a cost questionnaire (CQ) within four weeks of their accident. ASD participants exaggerated both the probability of negative events occurring, and the adverse cost of those events more than non-ASD participants. IES-Avoidance scores were the only significant predictors of both PQ and CQ scores. Findings are discussed in terms of the role of cognitive errors in posttraumatic adjustment.