Thermodynamic properties of ZrTe1.843 and Zr5Te4 have been measured by means of solution calorimetry, drop calorimetry, and adiabatic calorimetry. The thermodynamic functions for both compounds have been calculated. For ZrTe1.843 the following results are obtained : Delta(f)H(m) degrees(298.15 K) = -(295 +/- 7) kJ.mol(-1), S-m degrees(298.15 K) = (117.48 +/- 0.12) J.K-1.mol(-1) and {H-m degrees(T) - H-m degrees(298.15 K)}/(J.mol(-1)) = 68.2251.(T/K) + 4.48851.10(-3).(T/K)(2) + 26808.0.(T/K)(-1)-20830.2. For Zr5Te4 the results are : S-m degrees(298.15 K) = (330 +/- 0.4) J.K-1.mol(-1) and {H-m degrees(T) - H-m degrees(298.15 K)}/(J.mol(-1)) = 212.069/(T/K) + 22.2143.10(-3).(T/K)(2) + 314500.(T/K) - 66257.8. The results of the measurements on ZrTe1.843 are compared with previously reported measurements on ZrTe2.