The molar enthalpies of mixing (Δ mix H m ) of MCl-EuCl 2 (M = Na, K, Rb) liquid binary systems were measured at 1138 K over the whole composition range by direct calorimetry. A Calvet type calorimeter was used, and mixing of the two liquid components was achieved by the ampoule break-off technique under argon at atmospheric pressure. The enthalpy of mixing of these systems is negative over the whole composition range with a minimum of approximately -0.5, -3.5 and -4.5 kJ mol -1 for M = Na, K, Rb, respectively. The least-squares coefficients A, B, C in the equation A (kJ mol -1 ) = A + B x + C x 2 , where λ is an interaction parameter, are reported. From the trend observed in these MCl-EuCl 2 systems it was possible to estimate the mixing enthalpy of the CsCl-EuCl 2 system.