The molar enthalpies of solution of ZrTe3O8, TeO2, and ZrF4, in HF(aq) of concentration 10 mol . dm(-3) have been measured using an isoperibol calorimeter. From the results and other auxiliary quantities, the standard molar enthalpy of formation of ZrTe3O8(s) has been determined to be Delta(fm)(o)(298.15 K) = -(2119.2 +/- 9.6) kJ . mol(-1).