The viscosities of aqueous solutions of some poly(ethylene glycol)s (PEG) with nominal molecular weights ranging from 300 to 35 000 g mol(-1) were determined up to a concentration of 0.3 g cm(-3) at 298.15 K. From these data the intrinsic viscosity and the viscosity average molecular weight of the solute were calculated. The viscosity coefficients B were evaluated and hence the partial molar Gibbs free energy of activation of viscous Bow of solute at infinite dilution was calculated and interpreted in terms of the relative effects of solute on the ground and transition state solvent. The hydration numbers were determined and compared with available values in the literature.