In the solvent extraction system, the equilibrium molalities of ReO4-were measured at ionic strength from 0.2 to 2.0 mol kg(-1) in the aqueous phase containing NH4Cl as supporting electrolyte at temperatures from 278.15 K to 303.15 K. The standard extraction constants K-0 at various temperatures were obtained by methods of Debye-Huckel extrapolation and Pitzer polynomial approximation. Thermodynamic properties for the extraction process were calculated. (C) 2010 Elsevier B.V. All rights reserved.