Idiopathic inflammatory myopathies (IIMs) are a group of acquired diseases, characterized by immune-inflammatory processes primarily involving skeletal muscle. According to recent classification criteria, five major diseases have been identified: polymyositis (PM), dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), juvenile idiopathic myositis (JIM) and sporadic inclusion body myositis (sIBM). Although the etiology of IIMs is still incompletely understood, there is much evidence supporting the involvement of genetic, immunological, and environmental factors. In recent years, many new biomarkers have been identified as useful indicators for diagnosis, disease subtypes, prognosis, or response to treatment of IIMs. This article reviews the new biomarkers in serum and muscle tissue, focusing on their pathogenic, diagnostic and prognostic value in IIM. We assigned value based on the categories of myositis specific autoantibodies, cytokines, and genetic markers. (C) 2015 Elsevier B.V. All rights reserved.