Resistin, a newly discovered protein, promotes endothelial dysfunction and proinflammatory activation, contributing to subclinical atherosclerosis in different clinical settings. In this study we sought to investigate the relationship of increased resistin levels with estimated glomerular filtration rate (eGFR), the most established marker of kidney impairment, in hypertensive subjects. Our population consisted of 132 untreated non-diabetic subjects with stage I-II essential hypertension (49 males, mean age=54 years, office blood pressure (BP)=159/100 mm Hg). In all patients eGFR was assessed by the Modification in Renal Disease equation and venous blood sampling was performed for estimation of resistin concentrations. The distribution of resistin was split by the median (4.63 ng ml(-1)) and accordingly subjects were stratified into those with high and low values. Hypertensive patients with high (n=66) compared to those with low resistin (n=66) exhibited lower eGFR values (77.1+/-9.4 vs 89.1+/-12.2 ml min(-1) per 1.73m(2), P<0.0001), even after adjustment for established confounders. In the total population, resistin was associated with 24-h systolic BP (r=0.244, P<0.05), serum creatinine (r=0.311, P=0.007) and eGFR (r=-0.519, P<0.0001). Multiple regression analysis revealed that age (b=0.379, P=0.01), body mass index (b=0.158, P=0.022), 24-h systolic BP (b=0.284, P=0.006) and resistin (b=0.429, P<0.0001) were independent predictors of eGFR (R(2)=0.436, P<0.0001). In essential hypertensive subjects, higher resistin levels are associated with renal function impairment, as reflected by decreased eGFR. Moreover, the independent association of resistin with eGFR suggests involvement of resistin in the progression of kidney damage in the early stages of hypertension.