Preliminary reports are that plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) are higher in essential hypertensive patients than in normotensive controls, and that the urinary response to injected alpha human atrial natriuretic peptide (alpha-hANP) is augmented in essential hypertension. Further, there are reports of positive relationships between IR-ANP levels and arterial pressure. Confirmation is needed, however, with larger numbers of patients and with careful matching of diet electrolytes, age and sex, body posture, time of day, and other factors which may alter release or plasma clearance of atrial peptides. If indeed IR-ANP levels are raised in essential hypertension, it is possible that increased demands on the atria as a consequence of altered left ventricular structure and function lead to augmented secretion of atrial peptides. Whether the observed minor increases in plasma IR-ANP could have biologic effects to oppose pressor systems, to sustain glomerular filtration rate, and to suppress vasoactive hormone secretion, is unclear since the threshold level of IR-ANP which has biologic actions in man, is unknown. Plasma IR-ANP levels are raised in primary aldosteronism, and fall with treatment. These early reports suggest that atrial peptides might play a role in the pathophysiology of primary aldosteronism and perhaps essential hypertension, but much more information is needed.