Background: There is some evidence linking air pollution to cardiovascular morbidity. Our aim was to examine whether there is a correlation between air pollution and cardiovascular morbidity in the city of Trondheim, Norway., Material and Methods: We compared the mean daily number of admissions for cardiovascular disease to the St. Olav University hospital on days with relatively low and high levels of PM10 (1993-2001), PM2,5, NO, NO2, SO2, O3, toluene and paraxylene (1998-2001). A time series analysis was carried out to see how day-to-day variations in concentrations of air pollutants correlated with the number of hospitalizations for cardiovascular disease., Results: In the bivariate analysis, the mean daily number of hospitalizations was found to be significantly higher (p < 0.05) on days with NO and NO2 levels above the 80 th percentile (57.6 microg/m3 and 43.1 microg/m3, respectively) than on days with pollutant levels below the 20th percentile (11.3 microg/m3 and 16.9 microg/m3, respectively). Time series analysis did not show any statistically significant correlation between day-to-day variations in air pollution and hospital admissions for cardiovascular disease., Interpretation: The findings regarding NO2 and NO indicate that exposure to gases and/or ultra-small particles from diesel exhaust may influence cardiovascular morbidity.