The purpose is to provide a background for a discussion concerning the methods and values used in cost-benefit analysis in Sweden for air pollutions', from traffic, impact on human health and the research needs in this area. We provide an overview of the current state of the art of models used for and input needed for external cost calculations of the health impacts. The calculations are not straightforward and depend on the collaboration between several research disciplines. In the ExternE projects, which have been used as a reference point in this study, there are still uncertainties concerning which pollutants to take into consideration. Regarding the health impacts, we have recapitulated some of the main conclusions in a review by the American Heart Association (2010). They state that e.g. the following issues need further research: the importance of ultrafine particles, what constituent parts make traffic related air pollution more harmful than PM2.5 in general and the importance of coarse particles.