Background: Allogeneic transfusion confers a risk to the recipient and the recent introduction of leucocyte depleted blood has increased cost pressure on health resources. Colorectal surgery is a high blood usage field with 43% of all patients in our unit being transfused, over a three year period. Patient perceptions: Despite the risks associated with transfusion, a majority of patients are willing to have an allogeneic transfusion (85%) and think it is safe (89%), which may have implications in the uptake of alternatives available. The effect of bowel preparation Picolax bowel preparation causes significant dehydrating effects which may impair acute normovolaemic haemodilution (ANH). These effects can be minimised by administering intravenous normal saline. Acute normovoiaemic haemodilution (ANH) ANH significantly reduced allogeneic transfusion rate from 39% to 15% in the pilot study, however the controls were historical. No reduction in transfusion rate was seen (29% and 30%) in the prospective randomised controlled trial (n=160). Preoperative haemoglobin, blood loss, age, and transfusion protocol were the key factors influencing transfusion. The effect of ANH on coagulation ANH causes hypocoagulation, and this may explain why the expected red cell saving, as shown by mathematical modelling, was not seen in patients haemodiluted compared with controls.