Despite evidence that cardiac troponin I (cTnI) identifies patients with advanced heart failure (HF) at risk of death, data on heterogeneous HF populations are scarce. Our purpose was to verify and analyze the prognostic role of cTnI in acute HF patients admitted to the emergency department. This was an observational longitudinal prospective study carried out in an urban hospital. We studied 99 patients discharged from the department between March and December 2002 with a HF diagnosis and samples of cTnI. Patients with acute coronary syndromes, myocarditis or renal failure were excluded. The main outcome was death from any cause. The detection level of the cTnI assay was 0.05 ng/ml. cTnI was detected in 45.5% of HF patients. These patients had a higher NYHA class (P<0.001) at initial presentation and longer hospitalization (P=0.004) than cTnI-negative patients. Nineteen deaths occurred during the study: 17 for HF and 2 for acute coronary syndrome. Finally, detectable cTnI was associated with increased mortality risk (RR 4.7; 95% CI 1.3-17.1; P=0.021) also after adjustment for other adverse prognosis factors (age, NYHA class and presence of relapses). Our HF cTnI-positive patients had a worse clinical presentation and longer hospitalization. cTnI is a significant independent predictor of death and of longer hospitalization. It could be used for the early identification of HF patients at an increased risk of death in the long term, and of longer hospitalization. Thus, cTnI can aid decision-making and clinical management in the emergency department.