Abstract: A transfer bag apparatus is disclosed which is adapted to be used in the autologous transfusion of blood to a patient by collecting the blood from a primary blood reservoir (e.g., the collection chamber of a drainage device for the chest cavity of the patient or a cardiotomy reservoir). The transfer bag comprises a flexible bag, having means on one part of the bag to be placed in fluid-tight communication with an infusion set to transfuse the patient with blood, and spike means on another part of the bag adapted to be placed in fluid-tight communication with the interior of the primary blood reservoir to transfer blood to the interior of the blood bag.