Through the development of a general quantitative model for the understanding of the growth of continuous passivating films on metals it was possible to describe in detail the voltammetric growth of the NiO film on nickel in NaOH solutions. The transfer coefficient and the exchange current density at the Ni I NiO interface are about 1.5 and 4-8 mu A cm(-2), respectively, and vary with the NaOH concentration in the solution. The overpotential through the film always increases with the potential. The charge density of the film (proportional to its thickness) versus potential presents a sigmoidal behaviour. The electrical field inside the film lends first to a plateau followed by a new increase after the peak current density. In parallel, the ionic specific resistance inside the film passes through a minimum (at the peak potential) during the growth. As a whole it decreases with the increase of the growth velocity and passes through a minimum with the increase of NaOH concentration. All these facts are explained and in agreement with the proposed model.