Autoimmune reaction and inflammation observed in autoimmune diseases may be caused by the deregulated production of cytokines. Interleukin-6 (IL-6) is a pleiotropic cytokine with a wide range of biological activities such as support of hematopoiesis, regulation of acute phase reactions, and generation of immune responses. Uncontrolled hyperproduction of IL-6 causes plasmacytosis, hyper-gamma-globulinemia, thrombocytosis, mesangial cell proliferation of the kidney as well as inflammatory symptoms which are frequently observed in autoimmune diseases. Thus, interference with IL-6 signal transduction may be useful for autoimmune disease therapy. The pathogenic significance of IL-6 in autoimmune disorders and new therapeutic approaches involving blocking of IL-6 signal transduction are discussed.