Background-Tumor necrosis factor alpha-␣ (TNF-␣) activation is an independent prognostic indicator of mortality in patients with heart failure (HF). Despite the recognition that several TNF family cytokines are elevated during myocardial infarction, their role in predicting subsequent prognosis in these setting remains poorly understood. Methods and Results-We performed a systematic evaluation of TNF-␣ and its type 1 and 2 soluble receptors, together with interleukin (IL)-6, IL-1 receptor antagonist, and IL-10, in 184 patients (132 men; mean age, 64Ϯ12) consecutively admitted for myocardial infarction. We correlated their values to short-and long-term incidence of death and HF (primary outcome). In 10 patients, we also studied the presence of transcardiac gradients for TNF-␣ and its soluble receptors. The control group comprised 45 healthy subjects who were sex and age matched (33 men; mean age, 65Ϯ6 years) to the patients. All tested cytokines were increased in patients, and no transcardiac or systemic AV difference was found. After a median follow-up of 406 days (range, 346 to 696 days), 24 patients died and 32 developed HF. Univariate analysis showed that all cytokines were related to outcome, whereas after adjustment for baseline and clinical characteristics, sTNFR-1 remained the only independent predictor of death and HF (hazard ratio, 2.9; 95% CI, 1.9 to 3.8, tertile 1 versus 3), together with left ventricular ejection fraction, Killip class, and creatine kinase-MB at peak. Conclusions-sTNFR-1 is a major short-and long-term predictor of mortality and HF in patients with acute myocardial infarction. (Circulation. 2005;111:863-870.)