Patients with systemic juvenile rheumatoid arthritis (JRA) are often poorly responsive to existing therapeutic modalities. We evaluated the effectiveness of pulse therapy consisting of methylprednisolone 30 mg/kg/day for 3 consecutive days combined with cyclophosphamide 0.4 g/m2 body surface area on the 3rd day, for 18 patients with definite systemic JRA, who were enrolled in an open trial of 12 months' duration. The children received pulse therapy every 3 months; oral methotrexate 10 mg/m2 was started after the first pulse. A rapid and clinically significant suppression of systemic and articular manifestations was seen in all patients. Significant decreases in laboratory indices of disease activity were also observed. Side effects were minor and reversible. The results of our preliminary trial support the development of a controlled study to evaluate the efficacy of pulse therapy in systemic JRA.