Abstract—The objective was to study oxidative status, antioxidant activities, and reactive oxygen species byproducts in whole blood and mononuclear peripherals cells and their relationship with blood pressure. Sixty-six hypertensive patients and 16 normotensive volunteers as a control group were studied. In both, whole blood and peripheral mononuclear cells oxidized/reduced glutathione ratio and malondialdehyde was significantly higher, and the activity of superoxide dismutase, catalase, and glutathione peroxidase was significantly lower in hypertensive patients when compared with normal subjects. The content of damaged base 8-oxo-2′-deoxyguanosine in nuclear and mitochondrial deoxyribonucleoproteins of hypertensive subjects was also significantly higher than that of the normotensive control subjects. No differences in these measurements were found among hypertensive subjects grouped in tertiles of 24-hour average mean blood pressure or between “white-coat” and established hypertensive subjects. Furthermore, no relationship was observed between the average of 24-hour mean blood pressure and oxidized/reduced glutathione ratio, reactive oxygen species byproducts, malondialdehide, or genomic 8-oxo-2′-deoxyguanosine. In whole blood and in mononuclear cells from hypertensive subjects, there was an increase in oxidative stress and a reduction in the activity of antioxidant mechanisms that appeared to be independent of the blood pressure values.