Peripheral occlusive arterial disease (P.O.A.D.) is one of the situations in which hemorheological abnormalities are usually described. However the clinical relevance of hemorheological measurements in angiologic practice remains to be defined. The aim of the study was to investigate whether hemorheological disturbances are associated with alterations in oxygen diffusion and prognosis of the arterial disease. Three groups of patients were included in this work. First, a study was realized on 160 nondiabetic P.O.A.D patients (suffering from intermittent claudication to critical limb ischemia) in order to evaluate the possible influence of hemorheological disturbances on oxygen diffusion in distal tissue. A control group of 30 subjects matched for age and sex was also studied. A second study was performed on 80 diabetic P.O.A.D. patients (stage III and IV of Leriche and Fontaine classification) to determinate if hemorheological parameters could be considered as prognostic factors in the P.O.A.D. course. Hemorheological parameters were determined on different devices: red blood cell (RBC) aggregation by Myrenne aggregometer, blood and plasma viscosities by MT 90 falling ball viscometer. Transcutaneous oxygen pressure was measured by Radiometer TCM2 oxygen monitor. Several rheological parameters of non diabetic patients suffering from P.O.A.D. were significantly higher than those of control group subjects : blood viscosity (p < 0.05), plasma viscosity (p < 0.001), erythrocyte rigidity index (p < 0.01) and fibrinogen level (p < 0.0001). In the nondiabetic patients TcPO2 was negatively correlated with RBC aggregation, erythrocyte rigidity index and hematocrit /viscosity ratio. The diabetic patients who needed major amputation (above or below knee) presented significantly increased hemorheological parameters (blood viscosity, RBC aggregation, RBC rigidity index, hematocrit/viscosity ratio, fibrinogen level) compared to diabetic who had not been major amputated (no amputation or only toes' amputation). Our finding suggests that hemorheological factors (1) may influence oxygen transfer to distal tissues by maldistribution of blood flow and (2) may have prognostic significance in chronic peripheral occlusive arterial disease.