The existence of gaseous cobaltates of alkaline-earth metals was established in the present work by high-temperature mass spectrometry. Gaseous molecules: CaCoO2, SrCoO2 and BaCoO2 have been found for the first time. On the basis of the measured constants of the equilibrium of gas-phase reactions the standard enthalpies of formation: (-149 +/-19) kJ center dot mol(-1) (-149 +/- 20) kJ center dot mol(-1) and (-250 +/- 16)kJ center dot mol(-1); and standard atomization enthalpies: (1251 +/- 22) kJ center dot mol(-1), (1233 +/- 23) kJ mol(-1) and (1353 +/- 20) kJ center dot mol(-1) for CaCoO2, SrCoO2 and BaCoO2, respectively, have been defined. (c) 2004 Elsevier Ltd. All rights reserved.