“Massive” hemoptysis has been variably defined as production of more than 300 to 600 mL of blood in 12 to 24 hours, depending on the study. Although this connotation is perhaps important from a descriptive standpoint, the distinction has little clinical utility, as it is difficult for patients to accurately quantify the volume of blood they are producing, and the volume of hemoptysis may vary considerably from hour to hour (or even from minute to minute). In addition, some patients with diffuse pulmonary hemorrhage can present with life-threatening hypoxemia and diffuse parenchymal infiltrates, meeting all the criteria for the acute respiratory distress syndrome (ARDS), yet have no hemoptysis. Although any of the conditions listed in Table 41-1 may cause hemoptysis, those more commonly associated with massive hemoptysis are bronchiectasis, mycetoma, tuberculosis, bronchogenic carcinoma, lung abscess, and vascular-bronchial fistulas. A recent study of 29 patients from Singapore found that 62% had bronchiectasis, 13% had mycetomas, 10% had tuberculosis, 6% had tumors, and 3% had a pulmonary hemorrhage syndrome.1