Our experience with 56 patients who sustained massive transfusion exceeding two times their estimated blood volume is reviewed. Survival was 39% for the entire group, which included six cases of blunt multiple trauma and seven nontraumatic surgical emergencies, and 51% for the subgroup who sustained penetrating trauma. Six patients arrived without detectable vital signs, but half of them left the hospital alive. Three subgroups sustained 100% mortality: cirrhotics, nontraumatic surgical emergencies, and victims of blunt trauma. Thirty-eight per cent of the noncirrhotics developed a post-transfusion bleeding disorder, but the specific patients who would develop coagulopathy could not be predicted on the basis of any clinical parameter scrutinized, including lowest measured platelet count. Pulmonary morbidity was rare among penetrating trauma patients in spite of an average of 35 units of blood transfusion. Acute respiratory failure developed in a subgroup with penetrating trauma who received an average of 59 units of blood; blunt trauma patients developed acute respiratory failure at an average transfusion volume of 35 units. The 77% mortality among patients who developed coagulopathy, and our inability to predict in advance which patients will develop serious clinical bleeding, argue strongly in favor of an aggressive approach toward prophylaxis in these patients in spite of the theoretical risk of disease transmission from the additional units of platelets and frozen plasma required.