The idiopathic inflammatory myopathies represent a group ofimmunologically mediated diseases characterized by inflammation of skeletal muscle potentially leading to irreversible damage. On the basis of clinical, histological and immunological features dermatomyositis, polymyositis and sporadic inclusion-body myositis are recognized as separate entities. A definitive diagnosis of idiopathic inflammatory myopathies requires detailed histological, histochemical, immunohistochemical and electron-microscopic analysis of adequate muscle biopsy sample. However, in spite of thorough morphological analysis distinction of these disorders is not always straightforward and a close clinicopathological correlation is often essential to reach a correct diagnosis. Detailed morphological features ofidiopathic inflammatory myopathies and their relationship to pathogenesis is outlined.