Cardiopulmonary disease has been associated with particulate matter (PM) air pollution. There is evidence that exposure to elevated PM concentrations increases risk of acute ischemic heart disease events, alters cardiac autonomic function, and increases risk of arrhythmias. It is plausible, therefore, that PM exposure may exacerbate heart failure (HF). A case-crossover study design was used to explore associations between fine PM (PM(2.5): particles with an aerodynamic diameter < or =2.5 microm) and 2,628 HF hospitalizations. Patients lived on Utah's Wasatch Front and were drawn from those hospitalized at Intermountain Healthcare facilities with a primary diagnosis of HF. A 14-day lagged cumulative moving average of 10 microg/m(3) PM(2.5) was associated with a 13.1% (95% confidence interval 1.3 to 26.2) increase in HF admissions. The strongest PM(2.5)-HF associations were for elderly patients who had previously been admitted for HF and who required only a short period of hospitalization. HF hospitalizations are associated with lagged cumulative exposure to PM(2.5) of approximately 2 weeks. In conclusion, particulate air pollution may play a role in precipitating acute cardiac decompensation in otherwise well-managed patients with HF, perhaps through effects of PM on myocardial ischemia, cardiac autonomic function, and/or arrhythmic effects.