The extraction of rhenium(vii) with benzo-15-crown-5 (B15C5) and dibenzo-18-crown-6 (DB1SC6) into 1,2-dichloroethane was investigated. The presence of K+, NH4+or Na+in aqueous phase was necessary for the extraction. The study showed that the Re(VII) was extracted by forming ion-pair compounds of [M+(B18C6][Re4-] and [M+(B15C5)n][ReO4−](M+= K+, NH4+. and Na+; n = 1-2). Effea of cationic crown ether complexes on extraction of RcO4-is discussed in terms of structure of extracted species. It was found that K+-B15C5 cation is the most efficient since K+forms hydrophobic 1:2 complex readily with B1SCS. Equilibrium constants (Kex) and thermodynamic quantities for these extraction reactions were determined. The Kexvalues decrease in the sequences of K+> NH4+> Na+and B15C5 > DB18C6. The thermodynamic measurement indicated that the extraction of ReO4−with cationic B15C5 and DB18C6 complexes was enthalpy driven. The different extraction behaviors between anion species and alkali picrates are discussed.