The effect of pH on the colloidal stability of aqueous dispersions containing antimony-doped tin oxide (ATO) Or indium tin oxide (ITO) nanoparticles and poly(vinyl acetate-acrylic) copolymer (PVAc-co-acrylic) latex particles was investigated using experimental observations and Derjiaguin, Landau. Verwey and Overbeek (DLVO) theory. The microstructure, electrical properties and optical properties of composite coatings prepared from various dispersions were also studied. Zeta potential measurements revealed that the isoelectric point (IEP) of ATO nanoparticles was below pH 2.0, that of ITO nanoparticles was at pH similar to 6.0 and that of PVAc-co-acrylic latex was at pH - 2.0. ATO/PVAc-co-acrylic dispersions prepared at pH 3 were stable, but those prepared at pH 1.5 formed aggregates, which settled quickly with time. DLVO theory predictions are in accord with these results. Stable ITO/PVAc-co-acrylic dispersions are obtained at a pH of 3.0 and 11.0 but dispersions are not stable at a pH of 6.0. the IEP of ITO. At a pH of 3.0, DLVO results predict attraction between ITO particles and latex particles. Dispersion pH affected the microstructures laid properties of ATO (or ITO)/PVAc-co-acrylic coatings. Suspensions that formed aggregates produced coatings with lower percolation thresholds,aid lower transparencies than those produced from stable suspensions. (C) 2004 Elsevier Inc. All rights reserved.