The kinetics of GaAs thermal oxidation activated by (PbO + V ₂O₅) binary oxide compositions have been studied. The reciprocal influence between the activator oxides resulting in their nonlinear joint chemostimulating effect on GaAs thermal oxidation has been analyzed with allowance for the acid-base and redox properties of the oxides. A process mechanism has been advanced based on the study of the composition of resulting layers and the interactions in activator compositions performed by independent instrumental techniques (IR spectroscopy, X-ray fluorescence analysis, electron probe microanalysis (EPMA), atomic force microscopy, transmission electron microscopy (TEM), X-ray diffraction, and mass spectrometry).