In this work, the intrinsic viscosities of poly(vinyl pyrrolidone) with molar mass of 58 kg.mol(-1) were measured in water-ethanol solutions from (283.1 to 313.1) K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer-solvent interaction parameter, and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/ethanol are changed to the poorer solvents for poly(vinyl pyrrolidone) by increasing temperature. Also, the thermodynamic parameters indicate that water/ethanol are changed to the better solvents for poly(vinyl pyrrolidone) by increasing volume fractions of ethanol.