This paper deals with the formation of nickel distribution profiles in NiO/Al2O3 catalysts prepared by dry impregnation of spherical pellets of gamma-alumina with nickel nitrate aqueous solutions. The experimental concentration profiles were obtained and a mathematical model for the impregnation process was proposed and used to identify the main process parameters. The partial-differential equations of the model that describe the nickel concentration profiles and the fractional coverage were numerically solved. Backward finite-difference formulas were used to discretize the space variable and the resulting set of ordinary-differential equations was integrated with respect to time using a marching algorithm. The impregnation conditions determine the distribution of the active phase along the pellet. The concentration of the impregnation solution and the time of contact were important in the definition of the profiles, while the effect of the impregnation temperature was less significant. Satisfactory agreement was achieved between model predictions and experimental data, revealing that the simplifications assumed in the model are sound under the experimental conditions studied. (C) 2003 Elsevier Science B.V. All rights reserved.