The secretion pattern of human atrial natriuretic peptide (hANP) was investigated in 8 healthy male volunteers. Blood was drawn in 2 minute intervals for 90 minutes and in a second study in 4 minute intervals for 180 minutes. Base-line hANP plasma levels varied in a pulsatile secretion pattern of regular pulses every 9 +/- 1 minutes. Additionally long-term oscillations of 34 +/- 4 minutes were found. These data suggest that under basal conditions hANP varies in a pulsatile fashion.