Recent studies have identified the importance of biologically active molecules, such as neurohormones, as mediators of disease progression in heart failure. More recently, it has become apparent that, in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article will review recent clinical material that suggests that tumor necrosis factor, a pro-inflammatory cytokine, may contribute to disease progression in heart failure by virtue of the direct toxic effects that this molecule exerts on the heart and circulation. In addition, this article reviews the existing clinical literature, which suggests that cytokine antagonism is safe and potentially effective in patients with heart failure.