A case of a cavitary lung lesion in the right middle lobe of a 34-year-old woman who presented with hemoptysis is presented. The patient had a 2-year history of Wegener granulomatosis that had been treated with cyclophosphamide and corticosteroids. Although the patient gradually achieved remission of her disease, she developed new pulmonary symptoms and a cavitary lesion in her right lung. Further workup revealed elevated C- and P-ANCA titers. Following partial resection of her right lung, she was found to have an aspergilloma and no evidence of active Wegener granulomatosis. Pulmonary aspergillosis was felt to be the cause of both the hemoptysis and the cavitary lesion. We postulate that C-ANCA and P-ANCA were falsely positive in this case. Although rare, false positive C-ANCA and P-ANCA have been reported in pulmonary fungal infections.