Eosinophilic lung diseases typically present as a triad of pulmonary symptoms, an abnormal chest radiograph, and elevated levels of eosinophils in the sputum and lung tissue. This article focuses on primary causes of eosinophilic lung disease including acute eosinophilic pneumonia, chronic eosinophilic pneumonia, Churg-Strauss syndrome, and hypereosinophilic syndromes. In these disorders elevated eosinophil levels in the tissue lead to inflammation and tissue damage. Peripheral eosinophilia can often be measured when tissue levels are elevated but this is not as reliable a marker as tissue biopsy. Because corticosteroids act through a variety of mechanisms to inhibit eosinophil function and induce apoptosis, they are first-line therapy for eosinophilic lung diseases. Targeted immunosuppressive therapies, such as monoclonal antibodies against key regulatory cytokines for eosinophil production and survival, are not formally approved for eosinophilic lung disease but have shown promising results in published research studies.