Vaporizarion of gallium(III) phosphate under neutral and reductive conditions was studied by the Knudsen method with mass spectral analysis of the vapor phase. The process is accompanied by formation of gaseous PO₂, O₂, and GaPO₃; the condensed phase contains gallium oxide. The standard enthalpies of formation and atomization of gaseous GaPO₃ and GaPO₂ were determined.