Electrochemical behavior of the hexafluorouranate (UF6-) anion in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA) has been investigated at 298 K by means of cyclic voltammetry and chronoamperometry. Cyclic voltammograms of a Pt electrode revealed that electrochemical reduction of UF6- was an irreversible reaction to UF62- with alpha n(alpha) = 0.47. The diffusion coefficient of UF6- in BMImTFSA determined by chronoamperometry is 8.7 x 10(-8) cm(2) s(-1). The Stokes radius of UF6- in BMImTFSA is calculated to be 0.46 nm from the Stokes-Einstein equation using the diffusion coefficient and the viscosity of the melt. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3529875] All rights reserved.