BACKGROUND The barrier to long-term success after lung transplantation is the development of chronic lung allograft dysfunction. As the experience with lung transplantation accrues, it has become increasingly apparent that not all chronic allograft dysfunction is consistent with the traditionally recognized small-airway histological process of obliterative bronchiolitis (OB). OBJECTIVE To identify and describe chronic allograft dysfunction that is not consistent with the well-described bronchiolitis obliterans syndrome and to further characterize a novel histopathological process, acute fibrinoid organizing pneumonia (AFOP), that has led invariably to respiratory decline and death after lung transplantation. METHODS We evaluated 194 bilateral lung transplant recipients, identifying 87 individuals who developed chronic allograft dysfunction. They were then classified according to features on spirometry, chest imaging, and histopathological specimens. RESULTS Two main phenotypes of chronic allograft dysfunction were identified; 39 (45%) recipients were categorized as having developed OB and 22 (25%) as having AFOP. Survival in those who developed AFOP was significantly worse than in those who developed OB (median time to death 101 vs. 294 d; P = 0.02), with all exhibiting a rapid decline in respiratory function leading to death. CONCLUSIONS AFOP is a novel form of chronic allograft dysfunction exhibiting spirometric, radiological, and histopathological characteristics that differentiate it from OB. The further characterization of chronic allograft dysfunction and its heterogeneous manifestations will allow the targeting of clinical and experimental efforts to prevent and treat chronic allograft dysfunction.