Adipocytes secrete several biologically active substances that are presumed to be involved in obesity-related hypertension. There are no reports that deal with the relationship between plasma adiponectin concentration and blood pressure (BP). To evaluate the role of adiponectin in essential hypertension 33 patients with essential hypertensive (EHP) (12 women, 21 men) and 33 body mass index-matched normotensive healthy subjects (NHS) (13 women, 20 men) were studied. In EHP plasma adiponectin concentration was significantly lower than in NHS (9.1 +/- 4.5 v 13.7 +/- 5.2 microg/mL, respectively). In all subjects a significant negative correlation was found between plasma adiponectin concentration and mean, systolic, and diastolic BP, suggesting that adiponectin contributes to the clinical course of essential hypertension.