SUMMARY: Chronic pulmonary aspergillosis (CPA) is a refractory disorder that needs long-term antifungal treatment and occasionally results in fatal respiratory failure and hemoptysis. However, the pathological features of the disorder have not been thoroughly delineated. Thirty cases were therefore analyzed clinically and histologically to elucidate the pathophysiology of CPA. The subjects comprised 14 individuals who underwent surgical removal and 16 patients who died. No subject exhibited a severely immunocompromised state. The main symptoms included cough, hemosputum, and dyspnea. Chest computed tomography (CT) findings revealed a cavity, fungus ball, and consolidation and/or ground glass opacity (GGO); 27 serial CT scans showed enlarged consolidation and/or GGO (70z), dilatation of the cavity (26z), and extension to the opposite lung (22z). Histopathological findings revealed a cavity with ulceration, bronchitis, and various degrees of organizing pneumonia (OP) that were correlated with the area of consolidation and GGO on the CT scan. The essential pathophysiology of CPA can be understood as an active state of ulceration of the cavity and/or erosive bronchitis caused by contact with the fungus ball, which may play a significant role in the development of OP. Consequently, OP is thought to reflect respiratory failure that relates to the prognosis of CPA.