N. N. Firsova and M. A. Vyshlovab UDC 577.353:567.322:612.766 A simple substantiation of the application of backward light scattering to diagnostics of the aggregation state of blood has been proposed. It has been shown that the kinetics of spontaneous and shear aggregation obeys the kinetics of second order (Smolukhowski kinetics) and that the Smolukhowski constant is a function of the shape of an erythrocyte and the concentration of a high-molecular-weight polymer and it linearly depends on the rate of shear. The form of the dependence of the average size of erythrocyte aggregates on the rate of shear has been established. An expression for the apparent viscosity of blood as a function of the average size of an erythrocyte has been obtained; this expression has the form of a logarithmic asymptotics which remains constant with variation of the macromolecular composition of the plasma, the action of plasmapheresis, and the change in the hematocrit and enables one to determine both the rate of shear at which the process of disaggregation begins and the rate of shear in total disaggregation of erythrocytes and accordingly the maximum and minimum values of the viscosity of the blood. aRussian State Medical University, Moscow, Russia; email:; bInstitute of Rheumatology, Russian Academy of Medical Sciences, Moscow, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 76, No. 3, pp. 188-198, May-June, 2003. Original article submitted September 6, 2002.