Heart failure is a complex neurohumoral and inflammatory syndrome. Studies have shown that proinflammatory cytokines (interleukin-1, interleukin-2, interleukin-6, and tumor necrosis factor) are involved in cardiac depression and in the complex syndrome of heart failure. Understanding the involvement of these cytokines may enable us to reverse cardiac depression and heart failure with the use of monoclonal antibodies directed against specific cytokines that may block the downhill progression of heart failure. (Am Heart J 1998;135:181-6.)