The vaporization of Ti3O5 and V2O3 is studied by high-temperature mass spectrometry. Evaporation is carried out from Knudsen effusion cell made of tungsten. It is found that these oxides pass into vapor congruently with dissociation. Equations are obtained for the dependence of the partial pressures of molecular forms of the vapor on temperature in the form log p = -A/T + B.