Reports of the characterization and understanding of bronchiolitis obliterans organizing pneumonia (BOOP) have continued at an accelerated rate for several years. The radiographic and high-resolution CT features of BOOP continue to be documented. There have been new insights into the pathogenesis of BOOP. An animal model has been developed. Video-assisted thoracoscopic biopsy has become a standard for confirming the diagnosis. Childhood BOOP has been described in several reports. Idiopathic BOOP continues to be the most common type; however, a variety of clinical settings such as inhalation of mold spores and associated disorders such as renal transplantation continue to be described. This paper provides an update of advances in the pathogenesis, radiographic features, clinical course, and categorization of the heterogeneity of BOOP.