A mass spectrometric study of the vaporization of the compounds GeO2 hex and GeOam and of the mixture GeO2hex Gec made it possible to establish their mode of vaporization I GeO2hex - GeOg I2O2 II n GeOam - GeOng n1, 2, 3 III n2 GeO2hex n2 Gec - GeOng n 1, 2, 3. The enthalpies of vaporization at 298K are I 121.21.6 kcal mole II, n 1 53.41.0 kcalmole III, n 1 58.21.0 kcalmole. The polymerization energies at 298K are GeO-GeO 44.73.0 kcalmole GeO-GeO-GeO 88.55.0 kcalmole. Total pressures given in the literature were reinterpreted taking the presence of the polymers into account. The heat of formation of the metastable compound GeOam obtained is -59.6 0.7 kcalmole. The dissociation energy of the gaseous molecule GeO is 157.41.5 kcalmole.