The molar enthalpies of solution of CaTeO3, CaTe2O5, TeO2, and CaCO3 in HCl(aq, c = 11 mol.dm(-3)) have been measured by using an isoperibol calorimeter. From these results and other auxiliary data, the standard molar enthalpies of formation Delta(t)H(m)(o)(298.15 K) of CaTeO3(s) and CaTe2O5(s) have been calculated to be -(985.4 +/- 4.8) kJ.mol(-1) and -(1337.4 +/- 7.2)kJ.mol(-1), respectively. These values are consistent with the second law enthalpies of formation of the compounds determined in this laboratory by a transpiration technique.