Background: Epidemiological research into the role of traffic pollution on chronic respiratory and allergic disease has focused primarily on children. Studies in adults, in particular those based on objective outcomes such as bronchial hyperresponsiveness, skin sensitisation, and lung function, are limited. Methods: We have used an existing cohort of 2644 adults aged 18-70 living in Nottingham, UK, for whom baseline health and demographic data were collected in 1991 and computed two markers of exposure to traffic: distance between the home and nearest main road and modelled outdoor nitrogen dioxide (NO2) concentration at the home location. Using multiple regression techniques, we analysed cross-sectional associations with bronchial hyperresponsiveness, FEV1, spirometry-defined COPD, skin test positivity, total IgE and questionnaire-reported wheeze, asthma, eczema and hayfever in 2599 subjects, and longitudinal associations with decline in FEV1 in 1329 subjects followed-up nine years later in 2000. Results: There were no significant cross-sectional associations between home proximity to the roadside or NO2 level on any of the outcomes studied (adjusted OR of bronchial hyperresponsiveness in relation to living ≤150m vs >150m from a road = 0.92, 95% CI 0.68 to 1.24). Furthermore, neither exposure was associated with a significantly greater decline in FEV1 over time (adjusted mean difference in FEV1 for living ≤150m vs >150m of a road = 10.03ml, 95% CI, -33.98 to 54.04). Conclusions: This study found no evidence to suggest that living in close proximity to traffic is a major determinant of asthma, allergic disease or COPD in adults.