The enthalpy of solution of Cs5Te3 in (0.55 mol.dm(-3) NaClO + 0.5 mol.dm(-3) NaOH)(aq) was measured calorimetrically. In combination with auxiliary values the standard molar enthalpy of formation was derived : Delta(f)H(m)(o)(Cs5Te3,s,298.15 K) = -(942.2 +/- 8.3) kJ.mol(-1). The enthalpy increment of Cs5Te3 has been measured by drop calorimetry between T = 474 K and T = 856 K, and thermodynamic functions for Cs5Te3 have been calculated. A re-evaluation of the enthalpy of solution of tellurium has led to a slight correction of the previously reported standard molar enthalpy of formation of Cs2Te. The new value is : Delta(f)H(m)(o)(Cs2Te,s,298.15 K) = -(362.9 +/- 2.9) kJ.mol(-1).