Many strides were made in the field of blood transfusion before and during World War I. However, it was not until after the war that one of the most exciting and controversial episodes in the field of blood transfusion occurred. Review of the literature revealed the 1920s to be a tumultuous era filled with conflicting opinions concerning the safest method to perform blood transfusions. Early investigators used fresh unmodified blood for patient to patient transfusions. Later groups advocated the use of preserved blood for transfusions in order to permit its widespread availability. However, for many years, sodium citrate blood preservation techniques led to an unacceptable level of transfusion reactions. When bacterial pyrogens in the storage apparatus were identified as the source of side effects, the citrate method of transfusion gained widespread acceptance.