Interleukin 6 (IL-6) is a pleiotropic cytokine which has diverse biological activity, with wide-ranging effects on the immune system, homeostasis, and metabolism. It is the most abundant pro-inflammatory cytokine in the synovial joints and sera of patients with active rheumatoid arthritis (RA) and has been found to play a central role in the pathogenesis of the disease, causing joint inflammation and destruction, as well as systemic manifestations. Inhibition of IL-6 signalling has been investigated and developed as a potential treatment strategy for RA. Clinical trials have demonstrated the efficacy and safety of tocilizumab, a humanized monoclonal antibody directed against the IL-6 receptor, showing therapeutic benefit both in early RA and those considered to have refractory disease. The success of tocilizumab has spurred the development of an array of new biologic agents targeting the IL-6 pathway in RA.