The term eosinophilia denotes an absolute eosinophil count above 500 cells/microL. Eosinophilia has been noted in various inflammatory disorders: skin conditions (eczema, dermatitis, generalized drug reactions), malignancies (Hodgkin's disease and lung cancer), chronic granulomatous disorders (tuberculosis, sarcoidosis), fungal diseases (coccidioidomycosis, aspergillosis), drug- and chemical--related conditions, and idiopathic pulmonary infiltrate and eosinophilia syndromes. The incidence of pulmonary infiltration with eosinophilia is on the rise. Idiopathic pulmonary eosinophilia should be distinguished from the eosinophilic myeloproliferative syndrome. The diagnosis can usually be secured with the help of a good history and physical examination enhanced by simple laboratory tests on blood and sputum and a chest radiogram. The therapy is then directed to correct the initial injury.