OBJECTIVE To evaluate the efficacy and toxicity of cyclosporin A (CSA) in the treatment of refractory adult polymyositis/dermatomyositis (PM/DM). METHODS The province-wide British Columbia database for CSA use for persons with rheumatic diseases at Mary Pack Arthritis Centre was reviewed to identify all patients with PM/DM for the period January 1991 through June 1998. Also, a Medline search of English language literature was conducted for this topic from 1976 until January 1999, using the terms dermatomyositis, polymyositis, inflammatory myopathy, and cyclosporin A, and the reference lists of all papers were screened to include articles not identified by the Medline search. RESULTS In British Columbia, 172 CSA users of whom 6 had PM/DM were identified (4 PM, 2 DM). Previous therapy included high dose prednisone (N = 6), methotrexate (N = 4), azathioprine (N = 4), intravenous immunoglobulin (N = 3), and cyclophosphamide (N = 3). The mean CSA dose was 3.5 mg/kg/day. All patients improved. Creatinine kinase (CK) levels declined 52% from baseline. All 6 patients continued CSA a median of 6 months (range 3-44 mo) after initiation of therapy. Toxicity included an increase in serum creatinine > 30% of baseline in 3 patients and hypertension in one patient. The literature review identified an additional 59 cases. Forty-eight (81%) had a reduction in CK levels and improved clinically, 9/59 (15%) developed nephrotoxicity, 5/59 (8%) hypertension responsive to dose reduction, and 9/59 (15%) had hypertrichosis, gingival hyperplasia, or tremor. CONCLUSION Our population based experience with 6 patients and the 59 published cases suggests CSA is an effective therapy for resistant PM/DM, and toxicity is possibly more than expected in other rheumatic diseases.