The mechanism of deposition, from aqueous suspensions, of the Cr(VI) species on the surface of gamma-alumina used as support for preparing chromia supported catalysts has been investigated in the pH range 7.5-4.0. The joint use of adsorption experiments, potentiometric titrations, and microelectrophoresis allowed the proposition of a tentative deposition model. This model is then tested. The testing involved the derivation of various equations describing the deposition equilibria, the calculation (using an interactive code for calculating chemical equilibria) of the amount of the deposited Cr(VI) species, the calculation of the difference in the isotherms of the hydrogen adsorption in presence and absence of the Cr(VI) species, the calculation of the zeta-potential of the gamma-alumina particles in the Cr(VI) solutions, and the comparison of these parameters with the corresponding ones determined experimentally. According to the established model, the deposition of the CrO42-, HCrO4-, and Cr2O72- ions (being in the impregnating suspension) on the surface of gamma-Al2O3 occurs by adsorption of these ions on sites created by the protonated surface hydroxyls of the support on the inner Helmholtz plane (IHP) of the double layer developed between the support particles and the impregnating solution, as well as by reaction of the Cr(VI) species with the neutral surface hydroxyls of the support. In the pH range 7.5-6.1 the deposition by reaction prevails whereas in the pH range 5.7-4.0 both reaction and adsorption participate considerably to the whole deposition. Moreover, the decrease in the pH decreases the relative amount of the deposited CrO42- ions. The above were explained in terms of the variation, caused by the pH change, of the relative concentration of the CrO42-, Cr2O72-, and HCrO4- ions on the IHP and of the ratio [neutral surface hydroxyls]/[protonated surface hydroxyls]. Decrease in pH brought about an increase in the concentration of the neutral plus protonated surface hydroxyls and thus in the extent of deposition. It was found that, considerable lateral interactions are exerted between the adsorbed species. The progressive diminution of the mean basicity of the neutral surface hydroxyls as pH decreases explains the similar trend observed for the equilibrium constants related with the reaction of the aforementioned Cr(VI) species with the neutral surface hydroxyls. Finally, the random change, with pH, of the equilibrium constants related to the adsorption was attributed to the different trends followed by the Galvani potential on the surface and the Volta potential at the IHP.