The influence of polyethylene glycol (PEG) on the adsorption at zinc oxide/polymer solution interface has been determined. PEG macromolecules bond with the solid surface mainly via the -OH group of the surface of ZnO nanoparticles, which may interact with PEG through hydrogen bonding. Adsorption isotherms demonstrate the marked influence of the PEG molecular weight and the concentration of polymer solution on the extent of adsorption. The thickness of the adsorbed polymer layer on ZnO nanoparticles was calculated on the basis of measurements of their suspension viscosities in the absence and presence of adsorbed polymer. Results show that the thickness of the adsorption layer increased with increasing polymer molecular weight and the concentration of polymer solution. The main factors responsible for the changes in zeta potential were determined on the basis of the data obtained. The shift of the slippage plane away from the surface of ZnO nanoparticles plays major role below pH(iep). Above pH(iep), the blockage of the adsorption sites is the predominant factor. (C) 2004 Elsevier B.V. All rights reserved.