The purpose of the research was to study activation of free radical oxidizing processes and some metabolic shifts in patients with essential hypertension (EH) with long-term anamnesis of the disease and target organ
damages. In blood sera of patients with EH we defined indicators of free radical oxidations of proteins and lipids, a system of free radical protection, blood lipid spectrum, glycosylated haemoglobin, uric acid, fibrinogen, C-reactive protein. As control group we investigated blood of practically healthy subjects. It was shown that EH of ІІ stage is associated with moderate signs of oxidative stress, activation of free radical oxidations of proteins, in particular apoprotein fractions of atherogenic lipoproteins, development of insulin resistance, increase of C-reactive protein and uric acid and change of functional condition of NO-synthase systems with increased blood citrulline.