This study was designed to investigate whether endothelium-dependent reactive hyperemia (RH) is altered in patients with hypertensive disease (HD). In 35 mildly (HDI) patients, 38 hardly (HDII) patients, and 41 age-matched healthy subjects being as a control (C), forearm blood flow (FBF) was measured by means of impedance plethysmography before and after 30-second occlusion. Resting FBF was comparable in all groups while the maximal increase in FBF during RH was reduced in HD versus that in healthy. The difference in FBFmax between HDI and HDII was statistically significant showing the maximal vasodilatory reserve and consequently endothelial function to be dependent on the HD stage. Thus, the obtained data have indicated stage-dependent endothelial dysfunction in the patients with hypertensive disease. Designed method for evaluation of endothelial function by RH level may be successfully used in clinic for early and differential diagnostics of vascular disease.