The phase composition, anodic behaviour and semiconducting properties of the anodic film on Pb-6 6 at % As alloy have been investigated. The linear relationship between i and t-1/2 shows that the anodic film growth is controlled by a diffusion mechanism. The experimental results show that the anodic film contains t-PbO, PbO . PbSO4, 3PbO . PbSO4, and some arsenic compounds. The dielectric constant of the film is 2.8 x 10(2) obtained from the capacitance-time relationship measured at 2500 Hz. The Mott-Schottky plot shows that the film is an n-type semiconductor. The flat-band potential is -0.56 V vs Hg/Hg2SO4, and the donor density is 7.2 x 10(15) cm-3 for the film obtained at 0.9 V vs Hg/Hg2SO4 for 2 h on a Pb-6 at % As electrode.