Interleukin-6 (IL-6) is a pleiotropic cytokine that plays an important role in acute inflammation. It is secreted by T cells and macrophages during infection and after trauma. It is responsible for activation of B cells and other immune cells. In this book, the authors discuss the genetics, clinical applications and role in disease of interleukin-6. Topics include IL-6 inhibitors as novel generation of treatment strategies; the role of interleukin-6 in postoperative delirium; elevated interleukin-6 levels as a consequence of obesity and insulin resistance; the effects of IL-6 on respiratory mechanics in rats; and IL-6 targeting strategy for rheumatoid arthritis and various immune-mediated diseases.