Eosinophilic lung disease comprises a diverse group of disorders characterized by eosinophilic pulmonary infiltration in association with other inflammatory cells. In patients with respiratory symptoms, usually associated with radiographically documented infiltrates, blood eosinophilia is a helpful but inconsistent diagnostic finding. Currently diagnosis is confirmed more often by bronchoalveolar lavage than by lung biopsy. Possible etiologies include parasites, mycotic agents, drugs, and angeitis. Remaining cases are classified as idiopathic eosinophilic lung disease including Carrington's disease, idiopathic hypereosinophilic syndrome, acute eosinophilic pneumonia, and Loeffler's syndrome. Mild eosinophilia is also a possible finding of bronchoalveolar lavage in several other disorders but the role of eosinophils is less important. The prognosis and treatment of eosinophilic lung disease varies depending on etiology. Corticosteroids are frequently used but treatment modalities also depend on etiology.