The role of atrial pressure and catecholamines in secreting human atrial natriuretic polypeptides (hANP) were investigated in patients with acute or old myocardial infarction (AMI or OMI). No differences were observed in hANP levels obtained from brachial vein, right atrium, pulmonary artery and femoral artery, suggesting that hANP degradation in the pulmonary circulation has little clinical significance in hANP measurement. Plasma hANP levels in 10 patients with AMI were higher than those in controls and significantly correlated to both mean right atrial pressure (mRA) and pulmonary wedge pressure (PCW) (r = 0.76, p less than 0.05; r = 0.95; p less than 0.01, respectively). In 12 patients with OMI, plasma hANP levels were normal at rest and were significantly increased (p less than 0.01) with bicycle ergometer exercise associated with significant elevations of plasma catecholamine levels, mRA, and PCW. However, the increments of hANP correlated only to those of PCW. These results suggest that the elevation of atrial (principally left atrial) pressure rather than catecholamine stimulates hANP secretion.