The vaporisation of the NaCl-NdCl 3 system was investigated at 833-1116 K using Knudsen effusion mass spectrometry. The vapour species NaCl, NdCl 3 , and NaNdCl 4 were found in the equilibrium vapour and their partial pressures were evaluated. Theoretical calculations of the NaNdCl 4 (g) structure were performed and the thermodynamic functions of the complex species were evaluated. The enthalpy change of the dissociation reaction NaNdCl 4 (g)=NaCl(g)+NdCl 3 (g) was computed by the second and third law methods. The value of Δ d H o (298)=256.5+/-7.0 resulted from this computation. The volatility enhancement of NdCl 3 by the formation of the vapour complex NaNdCl 4 was estimated from obtained thermodynamic data of gaseous and condensed phases.