Systemic juvenile idiopathic arthritis is a heterogeneous form of arthritis in childhood and represents 10-20% of all juvenile idiopathic arthritides in the Caucasian populations of Northern America and Europe. Up to 30% of patients will still have active disease after 10 years, and morbidity within this group is high. Secondary complications (e.g. growth failure, osteoporosis, deformities, and loss of function) and amyloidosis are the medical sequelae, but there are also serious developmental and social consequences. The medical treatment of patients who are at the more severe end of the disease spectrum is unsatisfactory; however, new therapies that might improve prognosis, such as autologous stem-cell transplantation and approaches for blocking interleukin-6 signaling, are currently being assessed in clinical trials.