The method for determination of intracellular oxidants content has been proposed. The method is based on the analysis of changes of 2,7-dichlorodihydrofluorescein oxidation. The theoretical model of hydrogen peroxide diffusion and its consumption in the cell and quantitative determination of hydrogen peroxide gradient through the cellular membrane has been built taking into account the experimental data. The coefficient for H2O2 permeability through the plasma membrane of human amnion cells is (2.1 +/- 0.1) x 10(-4) cm x c(-1).