Eosinophilic bronchopneumopathy (EBP) is a disease characterized by eosinophilic infiltration of the lung and bronchial mucosa, as demonstrated by examination of bronchoalveolar lavage fluid cytologic preparations or histologic examination of the bronchial mucosa. Although the precise cause of EBP is unknown, a hypersensitivity to aeroallergens is suspected. The diagnosis relies on typical history and clinical signs, demonstration of bronchopulmonary eosinophilia by cytology or histopathologic examination, and exclusion of known causes of lower airway eosinophilia. Most dogs display an excellent response to oral corticosteroid therapy; however, side effects of this treatment can be limiting. New therapeutic approaches are being studied, including the use of aerosol therapy, cyclosporine, or drugs interfering with T helper 2 immune response.