Objective: The rheological properties of blood may constitute one of the 'parameters involved in the regulation of blood How such as the viscosity of blood at a given conditions which is determined by plasma viscosity, therefore the assessment of the concentrations of the plasma determinants of viscosity and RBCs aggregation (rheologic parameters) in diabetic patients with cardiovascular complications was the aim of this study. Subjects & methods : The clinical characteristics of the 80 diabetic patients with and without cardiovascular complications in correlation with assay* of some hcmorhcologic parameters was studied in this study: Measurement of FBS, and HbAlc; as an integrated index of diabetic control ,and the measurement of Lipid profile and Total serum protein were carried out , Plasma viscosity which was measured by the simple viscometcr suitable for detection of plasma viscosity was done and estimation of RBCs aggrcgation(aggrcgation time & rate) with the Laser scattering method in this study was employed for the studying the role of erythrocytcs aggregation in diabetic complications.