Invasive pulmonary aspergillosis is a specific form of pulmonary Aspergillus infection that occurs almost exclusively in immunocompromised patients. It differs both histologically and in its clinical course from classic aspergillomas. During a 5-year period (1986-1990), 8 patients underwent resection for cavitating invasive pulmonary aspergillosis that developed as a consequence of neutropenia during chemotherapy for malignancy. There were no perioperative deaths and no complications. This contrasts with reports of operation for classic aspergillomas. Histologic examination of the resected specimens showed that cavitating invasive pulmonary aspergillosis differed from classic aspergillomas. They consisted of necrotic lung tissue invaded by fungus with separation from the surrounding lung so that the sequestrum had the appearance of a fungus ball. Pulmonary aspergillosis is a common complication of profound neutropenia. The first hemoptysis in this group of patients is often life-threatening. The excellent results of operation in our series of patients may be attributed to their young age, good pulmonary function, and limited operation. This has lead us to recommend early surgical intervention in invasive aspergillosis once cavitation develops.