The viscosity of total venous blood was studied in 21 patients with osteonecrosis (ON) of the femoral head, and compared with the viscosity of 43 control patients, blood donors of the same mean age, and with the viscosity of 17 patients suffering from hip arthrosis. Measurements were carried out on a rotary resistance meter with coaxial cylinders. Along with the viscosity, certain biological, hematological and biochemical parameters, making up the main macro-rheological parameters, were measured in the same blood samples. Statistical analysis of the results confirms the hyperviscosity of total venous blood in patients with ON of the femoral head. This hyperviscosity does not seem correlated with the biological parameters studied, contrary to the viscosity of the blood in the control group. It is likely secondary to other factors, intrinsic to ON, and especially microrheological factors.