Purpose To acquire the tolerance, efficacy and safety indications of oral glucocorticoid and pulse intravenous cyclophosphamide (CTX) therapy for polymyositis (PM) or dermatomyositis (DM)patients, who are resistant ortolerant to glucocorticoid.Methods 20 patients were clinically and pathologically diagnosed as PM or DM according to the principle made by Bohan and Peter in 1975.Most of them were followed up for over 12 months with clinical manifestations, serum creatine kinase (CK) levels, electromyography (EMG) characteristics and muscle biopsy findings.All the adverse effects conforms to NCI-CTCAE 3.0.