The previously reported enhanced volatility of tellurium dioxide due to water vapor has been confirmed over the temperature range 825 to 970°K through vapor pressure measurements with a mass transport apparatus. Investigations of the temperature dependence of the characteristic equilibrium constant yield a value of 30.4 kcal/ mole for the heat of the (assumed) reaction TeO2(s) + H2O(g) = TeO(OH)2(g). Attempts to identify the gaseous hydroxide species through mass spectrometry were unsuccessful. Mass spectrometer studies of TeO2vapor, however, indicate ~20% dimer formation within the temperature range 920 to 1050°K.