Context: The heart failure (HF) syndrome is heterogeneous. While it can be defined by ejection fraction (EF) and diastolic function, data on the characteristics of HF in the community are scarce, as most studies are retrospective, hospital-based, and rely on clinically indicated tests. Further, diastolic function is seldom systematically assessed based on standardized techniques. Objective: To prospectively measure EF, diastolic function, and brain natriuretic peptide (BNP) in community residents with HF. Main Outcome Measures: Echocardiographic measures of EF and diastolic function, measurement of blood levels of BNP, and 6-month mortality. Design, Setting, and Participants: Olmsted County residents with incident or prevalent HF (inpatients or outpatients) between September 10, 2003, and October 27, 2005, were prospectively recruited to undergo assessment of EF and diastolic function by echocardiography and measurement of BNP. Results: A total of 556 study participants underwent echocardiography at HF diagnosis. Preserved EF (≥50%) was present in 308 (55%) and was associated with older age, female sex, and no history of myocardial infarction (all P<.001). Isolated diastolic dysfunction (diastolic dysfunction with preserved EF) was present in 242 (44%) patients. For patients with reduced EF, moderate or severe diastolic dysfunction was more common than when EF was preserved (odds ratio, 1.67; 95% confidence interval [CI], 1.11-2.51; P=.01). Both low EF and diastolic dysfunction were independently related to higher levels of BNP. At 6 months, mortality was 16% for both preserved and reduced EF (age- and sex-adjusted hazard ratio, 0.85; 95% CI, 0.61-1.19; P=.33 for preserved vs reduced EF). Conclusions: In the community, more than half of patients with HF have preserved EF, and isolated diastolic dysfunction is present in more than 40% of cases. Ejection fraction and diastolic dysfunction are independently related to higher levels of BNP. Heart failure with preserved EF is associated with a high mortality rate, comparable to that of patients with reduced EF.