Recent studies have identified the importance of biologically active molecules such as neurohormones in disease progression in heart failure. More recently, it has become apparent that, in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, is also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that cytokines such as tumor necrosis factor a, interleukin- 1, and interleukin-6, analogous to the role of the classic neurohormones, may represent another class of biologically active molecules responsible for the development and progression of heart failure. This article also looks at the early results of clinical trials that have utilized various cytokine antagonists in patients with heart failure...