Three of four recipients of transfusion in the United States are patients undergoing surgery, and despite promising advances in the development of alternatives to allogeneic blood transfusion, it is likely that for years to come this patient population will remain dependent on blood donated by volunteers. The safety of the blood supply has been questioned seriously since it became known that the human immunodeficiency virus could be transmitted by transfusion. In response to this threat, enforcement of strict donor eligibility criteria, removal of high risk donors from the donor pool, and testing of each donation with a panel of viral markers were instituted which have reduced the infectious risks of allogeneic blood transfusion dramatically during the last decade. The current safety of the blood supply is reviewed and the ongoing efforts to improve the safety of transfusions in the future are summarized briefly.