In the perioperative period, blood transfusions are most commonly administered to address acute blood loss resulting from trauma, neoplasia, or surgery. In this setting, transfusions may be life saving, allowing time for clotting or surgical hemostasis. In recent years, however, there is a growing awareness that the administration of blood products may not be a benign treatment. In addition to the more commonly cited complications such as transfusion reactions, disease transmission, and electrolyte disturbances, blood transfusions have also been linked to poor surgical outcomes, increased risk of infection, cancer recurrence, and acute lung injury. The recognition of these problems has lead to more conservative transfusion strategies, and questioning of what constitutes an appropriate transfusion trigger. In this section, we will discuss the pathophysiology of acute blood loss, the benefits and risks of transfusions in surgical patients, management of perioperative blood transfusions, and alternative strategies to minimize the need for blood products.