The role of atrial natriuretic peptide (ANP) in the pathogenesis of essential hypertension has not yet entirely been clarified. We investigated whether the increase of ANP in essential hypertension may be explained by elevated right atrial pressures and/or a different relationship between right atrial pressures and ANP secretion. Patients with stable essential hypertension undergoing right and left heart catheterization because of suspected coronary heart disease had significantly higher ANP levels than normotensives: 58.7 +/- 6.7 pg/ml in hypertensives versus 42.0 +/- 4.1 pg/ml in normotensives (p less than 0.01). Matching hypertensives with normotensives at identical levels of left ventricular enddiastolic pressure revealed significantly higher mean pulmonary artery pressures in hypertensives. Right atrial diastolic pressure (v-wave) after matching for LVEDP was 4.8 +/- 0.5 mm Hg in hypertensives and 3.1 +/- 0.2 mm Hg in normotensives (p less than 0.05). In addition, at any given mean right atrial pressure hypertensives showed higher ANP levels than normotensives. These results demonstrate that hypertensives exhibit raised pressures in the pulmonary artery independent of left ventricular pressure load. The elevation in right atrial pressures and the steeper relationship between these pressures and ANP are a suitable explanation for raised ANP levels in hypertension. ANP in essential hypertension may represent a counterregulation against elevated pulmonary resistance.