Dermatomyositis and polymyositis are the two major idiopathic inflammatory myopathies. The Bohan and Peter's criteria are still useful despite the probably different pathogenesis of the two myopathies. Cutaneous manifestations of dermatomyositis include heliotrope rash and Gottron's papules. The heliotrope rash, with or without edema, in a distribution involving periorbital skin is very suggestive of the diagnosis. Papules may be found overlying the "kneedle" of the hand or the elbows, knees, feet. Periungueal erythema with telangiectasis were characteristic but not pathognomonic. Scalp involvement is common. Skin lesions of dermatomyositis may precede the development of the myopathy and may persist after the control of the myositis. Some patients have an amyopathic dermatomyositis with normal muscle-enzyme, magnetic resonance scan and muscle biopsy. Muscle disease affects the proximal muscles, is generally symmetrical and symptoms are fatigue, weakness and sometimes myalgia. Proximal dysphagia reflects an involvement of striated muscle of the pharynx or proximal esophagus. Camptocormia reflects a severe involvement of paravertebral muscle. Other systemic features may be seen: pulmonary involvement (mostly interstitial pneumonitis and hypoventilation), arthralgias or arthritis, cardiac involvement, vasculatis and calcinosis particularly in children or adolescents with dermatomyositis. Malignant disease is associated with idiopathic inflammatory myopathies with a frequency of approximatively 10 to 15% in dermatomyositis and 5 to 10% in polymyositis and is strongly correlated with age, more than 50% of the patient over 65 years old were found to have a cancer. In the absence of malignant disease, the mainstay therapy for dermatomyositis and polymyositis is systemic corticosteroids (mostly 1mg/kg). In the lake of response or high dose dependance, intravenous immunoglobulins or immunosuppressive drugs like methotrexate or azathioprine may be discuss. Cyclophosphamide show some effectiveness in interstitial pneumonitis. Cyclosporin might be effective in children, less in adults. The efficacy of tacrolimus, mycophenolate mofetil, leflunomide and anti-TNF therapy need some prospective studies to determine if there are of value in idiopathic inflammatory myositis.