The process of anodic oxide growth has been investigated. It is shown that the obtained experimental results confirm the Fehlner-Mott oxidation model in the case of InSb, a typical compound of the 111-V group. We also present a kinetic theory of the anion migration in the formed oxide. The theory is based on the following assumptions.(a)The only species which moves through the formed oxide is the OH−anion.(b)The chemical reactions of OH−with In3+and Sb3+cations take place simultaneously and independently, in a thin layer of the oxide/InSb interface. The resulting solution of the kinetic equations describes the anion distribution in the formed oxide. A simple expression for the rate of oxidation is obtained. Another possible application of the presented theory is suggested.