The aqueous solution properties of poly(N-vinyl-2-pyrrolidone) (PVP)-denaturing agents (i.e., thiourea, guanidinium chloride, and carbonate) were studied by viscosity measurements. The polymer dimensions were calculated at 25 degrees C and at previously determined theta temperatures. The unperturbed dimension parameter, K-0, hydrodynamic expansion factor, alpha(eta), and unperturbed root-mean-square end-to-end distance, (1/2)(0), have been evaluated. Viscosimetrically determined characteristics (e.g. intrinsic viscosity, Huggins constants) and the high values of alpha(eta) and (1/2)(0) can be explained by the interaction between the polymer and denaturing agents.