The aim of the study was to investigate the release of natriuretic peptides during myocardial ischaemia and reperfusion associated with cardioplegic cardiac arrest. Brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) concentrations were measured in paired arterial, central venous and coronary sinus blood samples in 19 patients undergoing elective coronary artery bypass grafting before aortic crossclamping and 1, 5, 10 and 20 min after aortic declamping. Peak myocardial BNP release after aortic declamping was significantly higher than baseline values before aortic crossclamping. Both peak and cumulative BNP release during reperfusion correlated significantly with the severity of ischaemia, as assessed by myocardial lactate production. In 3 patients with perioperative myocardial ischaemia, cumulative and peak myocardial BNP release after aortic unclamping was markedly higher than in the remaining 16 uneventful patients. Myocardial ANP release during reperfusion was not significantly different from baseline values before aortic crossclamping. In conclusion, our data demonstrate a significantly enhanced myocardial BNP release early during reperfusion of the human heart after global ischaemia associated with cardioplegic cardiac arrest.