The quality of blood salvaged at operation and prepared with the Dideco Autotrans BT 795 autotransfusion device was compared with that of donor blood in 41 patients having cardiac surgery involving cardiopulmonary bypass. Saved blood had a higher haemoglobin concentration (17.3 v. 13.1 g dl-1; P less than 0.001), a higher 2,3-diphosphoglycerate concentration (5.3 v. 1.1 mmol litre-1; P less than 0.00001), higher white cell count (17.1 X 10(9) litre-1 v. 4.1; P less than 0.00001), higher pH (7.5 v. 6.6; P less than 0.00001) and a more physiological potassium concentration (5.4 v. 8.8 mmol litre-1; P less than 0.00001) than donor blood. Saved blood platelet count was 34.5 X 10(9) litre-1 compared with 146.24 X 10(9) litre-1 (P less than 0.00001) and its heparin concentration was 0.64 u. ml-1. We conclude that this autotransfusor is a useful aid to blood conservation, producing good quality red cells with relatively normal pH and potassium values. However, modification of the centrifugation and washing is required to lessen the high white cell count and heparin concentrations found in the saved blood.