From January 1, 1981 to December 31, 1992, we experienced nine patients with childhood onset of dermatomyositis and polymyositis. The mean age of disease onset was 12 years (range 7 to 16 years). Seven of them fulfilled the criteria of dermatomyositis, the remaining two were polymyositis. Girls were more predominant than boys in 6:3 ratio. The clinical features included extremities muscle weakness, skin rash, periorbital swelling and dysphagia. Increased muscle enzymes including creatine phosphokinase (CPK) or lactic dehydrogenase (LDH) were all positive in nine patients. All of our nine patients were treated with prednisolone after the diagnosis was established. The duration of treatment ranged from 3 to 65 months (mean: 25.3 months). Two of the nine patients also received immunosuppressive agents, hydroxychloroquine and azathioprine respectively. At present six patients survive without treatment. Two patients continue with corticosteroid and immunosuppressive therapy. One patient died from primary peritonitis, six months after being diagnosed with JDMS. In conclusion our study shows there is a female dominance; monocyclic clinical course is more common; and the prognosis is good in general, in the cases of juvenile dermatomyositis and polymyositis.