Laser Doppler velocimetry (LDV) and back scattering nephelometry techniques are used to study the dynamic properties of blood. These are determined significantly by the properties and the behavior of the erythrocytes in shear flow and are particularly manifested by the shapes of the velocity and of the concentration profiles of the directional streaming of blood in thin capillaries. These profiles are known to differ from those of simple homogeneous fluids. The potentialities of LDV are discussed to obtain the velocity profiles for the flow of the whole blood and of the erythrocytes suspensions at different hematocrites through horizontally positioned thin glass capillaries from 100 to 400 im in diameter. Possible artifacts are demonstrated inherent to LDV measurements of the velocity profiles due to the multiple scattering of laser light unavoidable in such thick layers of blood. Significant difference is experimentally obtained between the Brownian diffusion coefficient of the erythrocytes in suspension at the state of rest and their shear diffusion coefficient in the Couette flow. 1.