BACKGROUND: Although epidemiologic studies have shown an association between the total mass of particulate matter <2.5mum in aerodynamic diameter (PM(2.5)) and cardiovascular disease, few studies have examined PM(2.5) constituents associated with vascular and cardiac autonomic dysfunction. METHODS: In this longitudinal study, we investigated the relationship between PM(2.5) constituents and blood pressure (BP), and markers of the autonomic nervous system. In 466 elderly subjects residing in communities in Seoul, Korea, we examined 16 constituents, seven sources, and total mass concentrations of PM(2.5). We measured the BP, heart rate (HR), and indices of heart rate variability (HRV), such as the standard deviation of normal-to-normal intervals (SDNN), square root of the mean squared differences of successive NN intervals (rMSSD), and two frequency-domain variables (low frequency [LF] and high frequency [HF]). We used linear mixed effects models to assess the association of PM(2.5) constituents and sources with cardiovascular markers. RESULTS: BP, HR, and rMSSD were associated with concentration of total mass of PM(2.5). For each increase of the interquartile range in PM(2.5) constituents, systolic and diastolic BP, and HR increased by 2.1-3.3mmHg, 1.2-2.3mmHg, and 1.2-1.9bpm, respectively, while the rMSSD, LF, and HF decreased by 8.1-9.3%, 16.6%, and 20.4%, respectively. Particularly, elemental carbon, sulfate, ammonium, lead, and strontium in the PM(2.5) constituents and emissions from oil combustion and incineration were associated with increased BP, HR, and decreased HRV. CONCLUSIONS: Our results suggest an association between specific PM(2.5) constituents and vascular and cardiac autonomic functions. These findings may provide supportive evidence for developing a pollution reduction plan to prevent cardiovascular diseases.