Acute eosinophilic pneumonia, chronic eosinophilia, Churg-Strauss syndrome, and the hypereosinophilic syndrome are pulmonary eosinophilic syndromes characterized by an increased number of eosinophils in peripheral blood, in lung tissue, in sputum, in bronchoalveolar lavage fluid, or in all of these. These pulmonary eosinophilic syndromes generally are characterized by increased respiratory symptoms, abnormal radiographic appearance, and the potential for systemic manifestations. It is critical to exclude other causes of eosinophilia in patients who have lung disease, to make a quick diagnosis, and to treat aggressively with corticosteroids and other therapies to prevent long-term sequelae.