The standard molar enthalpies of formation of BaO(g) and SrO(g) have been obtained from an extensive literature assessment. Whereas the enthalpy of formation of BaO(g) obtained from the enthalpy of sublimation of BaO(s), is in good agreement with the dissociation energy, the values for SrO(g) are less unambiguous. The values obtained are Delta(f)H(m) degrees(298.15K) = -(112 +/- 5) kJ.mol(-1), and Delta(f)H(m) degrees (298.15K) = (1.5 +/- 15) kJ.mol(-1) for BaO(g) and SrO(g), respectively.