We estimated the nitrate/nitrite, carbonyl groups, reduced glutathione (GSH) and malondialdehyde (MDA) concentrations and Cu,Zn superoxide dismutase (SOD-1), catalase (CAT), glutathione peroxidase (cGSH-Px) and glutathione S-transferase (GST) activities in the blood of 17 normotensive young subjects (mean age 39+/-7.0 years), 21 normotensive elderly subjects (mean age 82+/-8.2 years) and 38 patients with essential arterial hypertension (mean age 73+/-8.0 years). Our examinations showed that hypertension in the elderly is associated with greater than normal levels of protein and lipid oxidation, decreased nitric oxide concentration and an imbalance in antioxidant status (decreased GSH concentration and SOD-1 activity). The increased activity of GST compensated the decreased activity of cGSH-Px in the blood of hypertensive patients. Our study confirms that the degree of oxidative stress in elderly patients intensifies, especially if said patients have associated essential arterial hypertension.