Enthalpy of dilution measurements were made for NdCl3(aq) over the molality range 0.0080 mol(.)kg(-1) to 2.6883 mol(.)kg(-1) at temperatures from 297.89 K to 372.08 K and at a fixed pressure of 0.5 MPa. Published values of osmotic coefficients, emfs of a reversible electrochemical cell, enthalpies of dilution, apparent molar heat capacities, and apparent molar volumes of NdCl3(aq) were critically assessed, and the more reliable of these results were combined with the present enthalpies of dilution to yield the parameters of an extended form of Pitzer's ion-interaction model valid to high molalities and for the temperature range 280 K to 375 K. Values of the solubility and enthalpy of solution of the hexahydrate crystal and the enthalpy of solution of the anhydrous crystal were also included in the data representation, leading to new standard properties for the solution processes of both of these crystal phases.