Transfusions are a life-saving intervention, but transfusion errors, particularly errors involving ABO incompatibility, can be deadly. Three actions that have frequently been a contributing cause for ABO incompatibility errors are incorrect labeling of the blood sample for crossmatching, incorrect interpretation by personnel in the blood bank, and incorrect identification of the patient prior to initiation of a transfusion. Laboratory staff and nurses who are involved in the administration of blood products must strictly follow facility policies to ensure that they give the correct blood product to the correct patient. The goal of this course is to provide information about blood incompatibility errors and the evidence-based practices to prevent them.