In this study we have investigated the efficacy and safety of cyclosporin A (CyA) in a group of pediatric patients with juvenile chronic arthritis (JCA, 9 cases) and polymyositis-dermatomyositis (PM-DM, 3 cases). Of the 9 JCA patients, 7 had the systemic and 2 the polyarticular form of the disease. All of the patients received CyA after the failure of corticosteroids and/or cytotoxic drugs. CyA was administered for 9 to 48 months at a mean dose of 5 mg/kg/day. Ten patients received corticosteroids with CyA. The results of CyA treatment were satisfactory overall, both in the PM-DM patients and in the JCA patients, as assessed by clinical and laboratory evaluation. CyA-related side effects included alopecia, hypertension, hypertrichosis, tremors, and hirsutism. One JCA patient developed polyserositis with hypoproteinemia of unknown origin while receiving CyA. CyA blood levels did not correlate with clinical efficacy and/or side effects. This study suggests that CyA represents a promising agent for the treatment of JCA and childhood PM-DM.