During essential and secondary arterial hypertension it is possible to observe changes in microcirculation perfusion associated with a reduction in tissue oxygenation due in part to hemorheological changes such as an increase in blood viscosity or the formation of the red blood cell "rouleaux" which favour an increase in peripheral resistance and can cause or worsen arterial hypertension. We studied 21 healthy subjects (11 male and 10 female aged 42 +/- 4) and 26 hypertensive subjects (14 male and 12 female aged 49 +/- 3). The patients were non smokers and non suffering from respiratory or haemathological pathologies. They were not undergoing antihypertensive or vasodilatory pharmaceutical treatment. The patients suffered from mild hypertension (II WHO) with Peripheral Occlusive Arterial Disease (POAD II "a" acc. to Leriche-Fontaine class.). The patients showed an increase in cholesterolaemia (6.42 +/- 0.81 mmol/l) and trygliceridaemia (2.73 +/- 0.09 mmol/l) at an average level. The patients were studied in standard conditions with a constant temperature of 22 degrees C. We measured SBP, DBP, MBP, and the HR. We also measured the elongation index (EI) (with shear stress range 0.30 to 30 pascals) using LORCA, acc. to Hardeman method (1994), in order to study the erythrocyte deformability and aggregation kinetics in dynamic condition. To evaluate deformability in static conditions we calculated the Erythrocyte Morphologic Index (EMI), acc. to Forconi method, via the bowl/discocyte ratio (for 100 red blood cells fixed in glutaraldehyde at 0.3% and observed with an optical microscope under immersion in glycerol). Peripheral oxygenation was taken transcutaneously (TcpO2). To establish the level of vascular disease we used the Regional Perfusion Index (RPI = TcpO2 foot/TcpO2 subclavean) and doppler guided Winsor Index (WI). The Student "t" test and linear regression were used for the statistical analysis. Our data confirm a reduction in peripheral tissue oxygenation in hypertensives especially if suffering from vascular disease which correlates significantly (p < 0.01) with a reduction in red blood cell deformability. This itself can increase peripheral resistances and favour the onset of hemorheological complications, at a cerebral-vascular level, which are frequent in hypertensives.