Phlebotomy errors leading to incompatible transfusions are a leading cause of transfusion-related morbidity and mortality. Our institution's specimen-labeling policy requires the collection date, 2 unique patient identifiers, and the ability to identify the phlebotomist. This policy, however, was initially strictly enforced only by the blood bank. In fiscal year 2005, following an educational campaign on proper specimen labeling, all clinical laboratories began strictly adhering to the specimen-labeling policy. Compared with the preceding 4 years, in the 3 years following policy implementation, the incidence of wrong blood in tube (WBIT) and mislabeled specimens detected by the blood bank decreased by 73.5% (0.034% to 0.009%; P < or = .0001) and by 84.6% (0.026% to 0.004%; P < or = .0001), respectively. During a short period, a simple, low-cost educational initiative and policy change can lead to statistically significant decreases in WBIT and mislabeled specimens received by the blood bank.