Background. There are controversial results regarding the endothelial function in patients with white coat hypertension (WCH). The aim of this study was to assess endothelial function measuring nitric oxide (NO) and C-reactive protein (CRP) level in WCH and to compare those with essential hypertension (EH) and healthy subjects. Methods. The 40 newly diagnosed patients with EH, 40 patients with WCH and 40 healthy volunteers were included to study. Plasma CRP levels were measured by immunonephelometery method. Plasma NO level was also detected by using the Griess method. Results. Plasma CRP level was significantly higher in patients with EH when compared with those with WCH and healthy subjects (6.3 +/- 2.1 mg/l, 2.1 +/- 0.9 mg/l and 1.6 +/- 1.3 mg/l, p < 0.05, respectively). However, there was no signifi cant difference with respect to CRP level between those with WCH and healthy subjects. NO level was significantly lower in patients with EH when compared with those with WCH and healthy subjects (4.6 +/- 1.1 mu mol/l, 6.9 +/- 1.2 mu mol/l and 8.1 +/- 1.5 mu mol/l, p < 0.05, respectively). There was no signifi cant difference with respect to NO level between those with WCH and healthy subjects. Plasma CRP level was positively correlated with office, daytime, night-time and 24-h blood pressure values, whereas NO level was inversely correlated with these parameters. Plasma CRP level was also inversely correlated with NO level. Conclusions. Our data suggest that CRP concentration is significantly higher and NO level is meaningfully lower in patients with essential hypertension when compared with those with WCH and controls. This may suggest that endothelial functions are preserved in patients with WCH in contrast to essential hypertension.