The intravenous administration of Hartmann's solution at a rate sufficient to maintain the hourly urine volume between 0.5 and 1.0 ml/kg/hr is recommended during major operations. Intra-operative extracellular volume expansion followed by the administration of sodium containing fluids for 48 hours postoperatively decreases the incidence of haemodynamic instability and acute renal failure and results in normal water and sodium excretion by the kidney throughout the peri-operative period. Abnormal extracellular volume may exist prior to induction of anaesthesia particularly in patients with pre-existing cardiovascular, renal and hepatic disease. In these patients the suggested fluid regime should be administered with care and may require diuretic therapy. If the operative blood loss in adults is less than one litre, no blood may be necessary. If the loss is between one and 2 litres packed red cells may be sufficient, whereas with a greater loss, filtered whole blood, coagulation factors and platelet infusions may be required. When possible, transfusions of stored autologous blood is recommended for elective operations.