The inflammatory myopathies are a heterogeneous group of diseases due to autoimmunitary or infective causes. They are diagnosed by clinical electrophysiological features, and muscle biopsy. The autoimmunity group is subdivided in dermatomyositis, polimyositis and inclusion body myositis. The second group caused by viral genesis are called generally "myositis". The two groups have a different prognosis and therapy. The infective group denominated myositis have usually a viral etiology. We have evaluated 6 patients with viral myositis that are studied by physical examination, blood test (CK included), electromyographic pattern and muscle biopsy. The Authors emphasized the role of muscle biopsy for the diagnosis of this pathology and in particular for the myositis.