The aim is to investigate the association between exposure to traffic pollution and development of asthma in adulthood. The pilot study includes 20 cases and 40 control subjects from the municipalities of Odense, Middelfart, Fredericia, Vejle and the County of Northern Jutland. Air pollution is calculated with the AirGIS system for residences, workplace as well as transportation to and from workplace. Funded by the Environmental Health Research Foundation for the Interior and Health Ministry (ISMF). Project period January 2004 to August 2005.