To study the effect of cardioprotection type on haemolysis, 100 patients scheduled for elective coronary artery bypass grafting were allocated to receive either blood cardioplegia (BCP) or crystalloid cardioplegia (CCP). Haemoglobin concentrations in plasma and urine were measured after induction of anaesthesia, 1 hour postoperatively and the next morning; blood acid-base status was determined at the end of cardiopulmonary perfusion; serum electrolytes and creatinine were measured before and 1 and 3 hours after the operation and serum creatinine also the next morning. Plasma haemoglobin values tended to be higher in the CCP than in the BCP group (47.6, 200.2 and 69.1 vs 31.5, 207.5 and 39.2 mg/l, p = 0.084). The urinary haemoglobin concentrations did not differ between the groups. The acid-base status showed greater buffer capacity with BCP technique. These results contradict association of blood cardioplegia technique with increased haemolysis during coronary artery bypass grafting.