Analysis of hospital lethality showed that hemorrhage was the cause of lethal outcomes in thoracic surgery among 0.5% of all hospitalized patients, 0.8% of those who underwent operation, and 17.3% of all patients who died. Among all fatal hemorrhages 28.6% were surgical and 71.4% were erosional. Surgical hemorrhage was due to injury inflicted to the large vessels (atria) during the operation. Erosional hemorrhages were caused by postoperative infectious-septic complications, progressive malignant tumors and pyo-purulent diseases, and exacerbation of peptic ulcer or the formation of an acute gastric ulcer. Among the principal causes of fatal hemorrhages are defective treatment (32.9% of cases), methodical and technical errors during the operation (28.6%), erroneous diagnosis (25.3%), initially severe condition of patients (6.6%), and progressive malignant tumor (6.6%). Intraoperative prevention of fatal surgical hemorrhage is based on personal experience, knowledge and skill of surgeons, and the use of modern technology in the control of blood loss. The prevention of erosional hemorrhage in patients who are not operated on consists in timely surgical treatment and early diagnosis in the postoperative period and active treatment of infectious-septic complications.