Best practice guidelines for blood transfusion in the feline species are well established and widely available.Despite this, xenotransfusion (the transfusion of blood from another species) of canine whole blood to cats is currently performed occasionally or routinely in some veterinary practices in several countries, including France, Italy and Australia (Caroline Véret and Séverine Tasker, personal communications).4 Veterinary surgeons may thus encounter feline cases having received such a transfusion and may need to know the expected outcomes of this procedure. There may also be emergency situations when dealing with an anaemic feline patient where compatible feline blood is not available and where a blood transfusion is required urgently. Considering the current lack of commercial availability of a haemoglobin-based oxygen carrier solution (such as Oxyglobin) as an alternative to compatible feline blood, there may be rare, but genuine, occasions where transfusion of a cat with canine whole blood or packed red blood cells may need to be considered as a life-saving procedure.