A 49-year old man developed myositis of the left masticatory muscles followed by myositis of the right supinator longus; these two lesions were histologically confirmed. Blood and bone marrow eosinophilia was present. Cure was obtained with systemic corticosteroids. Only one similar case was found in the literature. These cases differ from the various localized or focal forms of myositis as well as from eosinophilic polymyositis. Despite some similarities with masseteric myopathies in animals, no hypothesis can be formulated concerning the cause of the disease.