Pulmonary eosinophilia is a disease entity which is characterized by an increase of eosinophils in the bronchoalveolar lavage fluid or in tissue. While there are several disease states encountered in pulmonary eosinophilia, some have a definite cause and diagnosis, while others are of unknown etiology. The diagnosis of idiopathic eosinophilic pneumonia is given when other pulmonary eosinophilia with known cause and diagnosis are excluded. Simple pulmonary eosinophilia and chronic eosinophilic pneumonia are well established disease entities, but recent papers have clarified a new concept of acute eosinophilic pneumonia. In this article, the clinical features of three idiopathic eosinophilic pneumonias simple pulmonary eosinophilia as a self-limiting lung infiltrates, chronic eosinophilic pneumonia as a disease with longstanding symptoms requiring steroids administration and a tendency to relapse, and acute eosinophilic pneumonia as an acute respiratory distress which responds dramatically to steroids administration and without relapse after discontinuation of therapy are discussed.