Hypertension is associated with microcirculatory impairment. Our objectives were to evaluate endothelial function and inflammatory biomarkers in patients with resistant (RH) and mild to moderate (MMH) arterial hypertension in comparison to normotensives (control group-CG). Three groups, 25 patients each, have been investigated, by anamnesis, venous occlusion plethysmography (VOP) and serum determination of adhesion molecules (VCAM, ICAM), adiponectin, endothelin and C-reactive protein (CRP). Patients not using statins and with or without blood pressure control were also analyzed. RH group showed smaller percentage increase of maximum forearm blood flow (FBF) (endothelial-dependent vasodilatation) than controls (p < 0.05), but no significant difference could be detected between MMH and CG groups on maximum FBF and minimum vascular resistance post-ischemia. RH and MMH groups showed higher resistance averages compared to controls (p < 0.05). Uncontrolled BP in hypertensive patients showed worse results for blood flow and resistance. Endothelial-independent vasodilatation was not affected. Endothelin levels were higher in RH and MMH groups (p < 0.05) not using statins. CRP was significantly higher only in RH compared to CG (p < 0.05). In conclusion patients with severe hypertension and lack of blood pressure control showed greater impairment of endothelial function with higher CRP and endothelin levels.