Seventy-five children with definite JDMS will be enrolled in a 24-month prospective, randomized, multicentered trial comparing 3 treatments: oral prednisone (P), combination of oral prednisone and methotrexate (P/MTX), and combination of oral prednisone and etanercept (P/E). Primary response measures will be muscle strength and mean duration of steroid therapy. Secondary response variables are disability in daily function and height and weight growth velocity (steroid toxicity measures). The combination of P/E will be tested and compared to both P alone and the combination of P/MTX after 3, 6, 12, 18, and 24 months of treatment. In addition, the combination of P/MTX will be compared to P alone after 3, 6, 12, 18, and 24 months of treatment. In pretreatment muscle biopsies, proangiogenic factors (such as vascular endothelial cell growth factor and basic fibroblast growth factor), angiostatic factors (such as angiostatin and endostatin), and vascular morphology (vessel number, width, length and area) will be quantified and tested for ability to predict muscle strength and functional ability 3, 6, 12, 18, and 24 months later.