Eosinophilic myositis is a rare entity accompanying parasitic infection or other inflammatory disorders. Two cases are reported in which myalgia and eosinophilic infiltration of muscle occurred in the absence of associated disease, and twelve previously published cases of idiopathic eosinophilic myositis are reviewed. A classification system for idiopathic eosinophilic muscle disease is proposed, describing three distinct groups. Comparisons are drawn between these and other causes of eosinophilic muscle disease, outlining the differential diagnoses for each group.