The first successful transfusion of blood from one dog to another was first reported in 1665 by Richard Lower. He anastomosed a carotid artery of a donor dog to the jugular vein of an acutely bled recipient. At this time in history, blood was regarded as the essence of life and useful only for its alleged psychic effects. It wasn't until 1818 that whole blood was used for its intrinsic value when a London obstetrician initiated blood replacement therapy for postpartum hemorrhage. As veterinary critical care becomes more and more sophisticated, the advantages of a basic knowledge of transfusion therapy and blood banking are increasingly apparent. The purpose of this article is to offer current knowledge on: 1) storing blood, 2) selection of donors, 3) blood grouping and crossmatching, 4) blood collection, 5) indications for component transfusions, 6) administration, and 7) complications.