['Allopurinol protects the heart against ischaemic events during coronary artery bypass grafting (CABG), possibly because of its antioxidant properties. This double-blind study was designed to investigate whether allopurinol (1 g), given before cardiopulmonary bypass and prior to the opening of cross-clamping, has an antioxidant effect in CABG patients by measuring plasma total peroxyl radical scavenging capacity.', 'Twenty-seven patients with stabile angina were randomized into allopurinol (n = 14) or placebo (n = 13) groups.', 'During 10 min reperfusion, plasma hypoxanthine and xanthine concentrations increased only in the allopurinol group, whereas uric acid concentrations decreased. Total peroxyl radical scavenging capacity (TRAP) decreased from the initial value at all measuring points in both groups.'] Does allopurinol increase free radical scavenging capacity during reperfusion in coronary artery bypass graft patients?