The growth of porous aluminium anodic oxide films on 99.5%, 99.99% and 99.999% purity Al metal in stirred dilute phosphoric acid solutions (0.005-0.4 mol l(-1)) at 2-20 degreesC temperature and relative high anodizing voltages was studied. A kinetic model is proposed for solutions of concentration up to 0.1 mol l(-1). The size of cells in the films formed in dilute phosphoric acid solution varies linearly with the anodizing voltage with a proportionality coefficient varying from 2.67 to 2.25 at electrolyte concentrations from 0.2 to 0.025 mol l(-1), respectively. On the basis of the variation of oxide film mass, current density and Al volume expansion factor with anodizing time, conditions for the formation of highly ordered pore arrays may be predicted.