The anodic oxidation of Sb in H3PO4 solutions is studied within the frame of an investigation concerning the mechanism of the initial stages of anodic film growth on metals. In this special case, so-called induction periods of constant potential preceding the quasi-linear potential rise in a galvanostatic experiment are explained by a semiconductor layer formation on the Sb electrode. Proofs for this suggestion are furnished by determining the main electrochemical and electrophysical characteristics of the film, both during its growth and in steady-state conditions. These parameters include field strength, ionic conductivity, thickness, potential of zero photocurrent, photocurrent onset energy, dielectric constant and diffusion coefficient of charge carriers in steady-state conditions.