Pulmonary aspergillosis is a rare disease, most commonly presenting as secondary invasion of pre-existing cavitary disease. In Toronto General Hospital 24 patients have been recognized as having this disorder in the 10 years from 1965 to 1975. The most common presenting symptoms were cough, sputum production, and hemoptysis, with the hemoptysis occasionally being massive. Tuberculosis and bronchiectasis were the commonest pre-existing diseases. Thirteen of these patients were treated by surgical resection because of major complications or progression of the aspergillosis. Five of these patients died following surgery, all of these having had major complications prior to surgical intervention. Of the eight surviving patients seven are progressing well, but one had developed further extension of his disease.