Eleven patients with idiopathic inflammatory myopathy refractory to treatment with corticosteroids and other immunosuppressive agents were treated with monthly intravenous cyclophosphamide (0.75-1.357 g/m2). Six patients completed a full course of 7 infusions at which point only one patient met predefined criteria for improvement in both strength and function. Five had modest improvement in strength but did not meet the criteria for improvement. All patients have subsequently required treatment with other medications. Major complications observed during therapy included serious infections in 2 patients (streptococcal endocarditis and disseminated Mycobacterium avium intracellulare) and death in one patient in which the contribution of cyclophosphamide cannot be excluded. We conclude that intravenous cyclophosphamide as used in our study cannot be recommended for the treatment of patients with refractory inflammatory myopathy.