During the period 1969 to 1974, 41 patients having cultures positive for aspergillus were seen on the thoracic surgical services of the University of Maryland and Mt. Wilson State Hospitals. Intracavitary mycetoma was present in 36 patients. In 32 the underlying disease was chronic cavitary tuberculosis, 5 had decreased immunity due to other diseases, and in 3 no underlying disease was noted. One final patient developed a mycetoma following repair of tetralogy of Fallot. Hemoptysis, the predominant symptom, occurred in 23 patients, all of whom were from the group with intracavitary mycetoma. Hemoptysis was life-threatening in 8 patients, severe but not life-threatening in 12, and minimal in 3. Fifteen patients underwent pulmonary resection with 2 deaths. Both patients who died had undergone emergency resection for life-threatening hemoptysis; the fungus ball had developed following a previous resection for tuberculosis, and both had poor pulmonary reserve. Of 10 patients with hemoptysis who were not treated surgically, chiefly because they were poor operative risks, 4 died. This study suggests that pulmonary aspergillosis, particularly of the intracavitary type, is a potentially life-threatening disease. Because of the suddenness with which massive hemoptysis may occur, pulmonary resection is recommended for all patients with intracavitary mycetoma who do not constitute prohibitive operative risks.