Formation thermodynamics have been investigated for the vapour complexes DyAlvCl3v+3 by quenching experiments within the range T = (654 to 847) K and p/p degrees) = (0.4 to 1.8). The results showed that DyAl3Cl12 was the predominant vapour in the system (DyCl3 + AlCl3). The changes of enthalpy and entropy for the reaction {DyCl3(s) + (v/2)Al2Cl6(g) = DyAlvCl3v+3(g)}, calculated from the quenching experiments, were Delta(r)H(m) degrees(DyAl3Cl12, g, 298.15 K) = (17 +/- 2) kJ . mol(-1), Delta(r)S(m) degrees(DyAl3Cl12, g, 298.15 K) = -(11 +/- 3) J . K-1 . mol(-1), Delta(r)H(m) degrees(DyAl2Cl9, g, 298.15 K) = (92 +/- 5) kJ . mol(-1), and Delta(r)S(m) degrees(DyAl2Cl9, g, 298.15 K) = (68 +/- 7) J . K-1 . mol(-1), respectively.