Whereas preventive interventions for primary care physicians are now well established, the preventive interventions in emergency departments have been only partially and recently evaluated. Emergency departments probably represent however an opportunity for preventive medicine. Indeed, the population, sometimes vulnerable, consulting emergency departments, frequently presents risks factors and risks behaviours. Moreover, the concept of "teachable moment" and the studies recently performed seem to confirm this hypothesis. This article review the currently preventive interventions recommended in emergency departments and discuss the rationale to implement preventive medicine in emergency departments and the limits of this process.