During a retrospective analysis of 877 cases of lung cancer, we explored the relationships between cell type, site, cavitation, varying degrees of hemoptysis, and radiation therapy. Massive terminal hemoptysis (29 cases) was found to be significantly associated with cavitated (P less than 0.0001 squamous cell carcinoma (P = 0.0002), ARISING IN EITHER THE RIGHT OR LEFT MAIN BRONCHI (P less than 0.0001). Lesser, nonlethal degrees of hemoptysis (140 cases) were not cell-type associated, occurring in approximately 15% of cases of all major tumor types. Radiotherapy, although employed more frequently in the massive-hemoptysis population, did not appear to be causally related to hemoptysis of any degree. An interesting case, which provoked the above study, is described: a patient with bronchogenic squamous cell carcinoma and terminal hemoptysis due to a tumor fistula between the primary lesion and the left atrial chamber. The forms of cardiac involvement in lung cancer are discussed.