The effect of the solvent composition on the conformation of a super high molar mass polyelectrolyte, M-w = 22-25 X 10(6), dissolved in a water-acetone mixture was investigated using static and dynamic light scattering. When increasing the concentration of acetone above 80 mass percent, a reversible conformational change of macromolecules occurs, which causes a sharp decrease in the viscosity, a rise in the light scattering intensity, and also a decrease in the radius of gyration, R-g, the hydrodynamic radius, Rh, as well as in the second virial coefficient A(2). The correlation function measured by dynamic light scattering changes from bimodal to unimodal indicating the formation of compact globular structures.