The voltammetric method of antioxidant activity estimation proposed in recent studies by Korotkova et al. [J. Phys. Chem. 74 (2000) 1544; J. Electroanal. Chem. 518 (2002) 56; Anal. Bioanal. Chem. 375 (2003) 465] is based on the decrease of the electroreduction oxygen current in the presence of the antioxidant. The further development of the theory of this process has been carried out using the kinetic current theory for conditions of direct current voltammetry at a given potential. A mechanism for the decrease of the electroreduction oxygen current in the presence of an antioxidant has been proposed. Equations of the diffusion and kinetic currents for reversible, quasi-reversible and irreversible processes have been found. These equations made it possible to analyze parameters influencing the sensitivity of the method for estimation of the antioxidant activity and to indicate the means of its optimization. (C) 2004 Elsevier B.V. All rights reserved.