The inflammatory myopathies, commonly described as idiopathic, are the largest group of acquired and potentially treatable myopathies. Dermatomyositis and polymyositis are generally responsive to immunosuppressive therapies, but could be refractory to them. Therapeutic plasma exchanges (TPE) have been used for three decades to treat autoimmune diseases. Their mechanism of action, which hinges on profound modulation of the immune system, is only partially understood. Despite the absence of supportive evidence provided by controlled trials, some observations suggest that TPE could have a role to play in the therapeutic strategy for refractory inflammatory myopathies, especially acute forms. TPE should probably be indicated preferentially for refractory and acute inflammatory myopathies, in combination with immunosuppression and/or anti-B-lymphocyte therapy.