OBJECTIVES: To investigate if the population living along streets with high traffic density has a higher prevalence of chronic respiratory symptoms. METHODS: A sample of 673 adults and 106 children (0-15 years), living along busy traffic streets in the city of Haarlem was compared with a control sample of 812 adults and 185 children living along quiet streets. Exposed and control streets were selected on the basis of model calculations of NO2 concentrations. A postal questionnaire containing questions about respiratory symptoms and several potential confounders was used to collect information from the study subjects. RESULTS: After adjustment for potential confounders, children living along busy streets were found to have a higher prevalence of most respiratory symptoms than children living along quiet streets. Adjusted odds ratios were significant for wheeze and for respiratory medication used. Risk ratios were higher for girls than for boys, with significant adjusted odds ratios between 2.9 and 15.8 for girls. In adults, only mild dyspnoea was more often reported by subjects living along streets with high traffic density. CONCLUSIONS: The results suggest that living along busy streets increases the risk of developing chronic respiratory symptoms in children.