Abstract Evidence regarding the association of blood transfusions with recurrence of solid tumours is largely conflicting. This is perhaps unsurprising given the retrospective nature of the studies performed to date, the complexity of the disease and its treatment, and variations in local transfusion practices. Nonetheless, new data demonstrating that transfusions of whole blood, as opposed to red cell concentrates, are associated with earlier cancer recurrence are most readily explained by a cause and effect relationship. There is a growing literature documenting previously unforeseen immunologic consequences of homologous blood transfusion. These possible clinical consequences include earlier cancer recurrence and increased susceptibility to infection with bacteria and viruses. The questions raised in this review can be answered conclusively only by controlled prospective studies. For the present the prudent clinician will select red blood cells rather than whole blood for transfusion, employ autologous transfusions whenever feasible, and recognize that blood transfusion is a therapy with considerable benefits, but also considerable risks.