Cryptogenic bronchiolitis is a unique clinical disorder that causes rapidly progressive, chronic airflow obstruction. In this article, we reviewed the pathology, clinical characteristics, and proposed pathogenesis of cryptogenic bronchiolitis. It is evident that cryptogenic bronchiolitis represents the result of a disordered inflammatory response in the small airways of the lung. The clinical characteristics of cryptogenic bronchiolitis, in most instances, should allow this disorder to be distinguished from other causes of chronic airflow obstruction, as well as from BOOP. In this regard, a high clinical suspicion and an awareness of its unique clinical features are the keys to the diagnosis of cryptogenic bronchiolitis.