Dermatomyositis (DM) is an idiopathic inflammatory disorder consisting of skin and skeletal muscle involvement. Patients with skeletal muscle involvement have polymyositis (PM), and those unresponsive to therapy and with characteristic findings on muscle biopsy have inclusion body myositis. Patients without muscle damage and typical skin lesions have amyopathic dermatomyositis. Disease in children (juvenile dermatomyositis) is not associated with malignancy as it may be in adults (paraneoplastic dermatomyositis). Overlap syndrome (OS) is mixed connective tissue disease combining some features of DM, SS and LES. Scleromyositis is overlap syndrome associated with anti-PM-Sci antibodies. Patients with PM, DM or OS with "interstitial lung disease" and anti-synthetase antibodies have an "anti-synthetase syndrome". Various drugs, including d-penicillamine, NSAIDs, anti-infectious agents, as well as lipid lowering drugs, the HMG-CoA reductase inhibitors may cause myopathy and skin lesions (drug induced dermatomyositis). "Dermatomyositis" occurring as adverse reactions of drugs are rare, irregular and impossible to predict in individual patients. They are very interesting in that they may be keys for explaining the pathogenic mechanisms of the disease.