The Interleukin 6 (IL-6) family is a large and diverse group of cytokines (IL-6, IL-11, IL-27, IL-31, OSM, LIF, CNTF, CT-1 and CLCF1) that is defined based on the use of common β-receptor signaling subunits. This family is very complex and affects most, if not all, major biological systems of the body. Its individual members are involved in reproduction, development tissue regeneration, immune homeostasis and defense against infection, trauma and injury. Not surprisingly, dysfunction in IL-6 family can lead to severe consequences such as chronic disease and cancer, which make them good candidates as diagnostic indicators, disease biomarkers and therapeutic targets.