The clinical courses of 11 cases of eosinophilic pneumonia which were clinico-pathohistologically diagnosed and found to be unassociated with organic disorders producing peripheral blood eosinophilia were extensively investigated and compared with various types of eosinophilic pneumonia previously reported. Five cases of acute eosinophilic pneumonia fulfilled the following criteria: 1) less than a one-month history of symptoms prior to diagnosis, 2) a short clinical course and 3) no recurrence. Six cases of chronic eosinophilic pneumonia fulfilled the following criteria: 1) more than a two-month history of symptoms prior to diagnosis, 2) a prolonged clinical course and 3) recurrence. The results suggested that various types of previously reported eosinophilic pneumonia classified by sex, the presence or absence of peripheral blood eosinophilia, the degree of clinical symptoms or peripheral blood eosinophilia, and the degree of abnormalities on chest X-ray films should be extensively reevaluated.