Irradiation at 254 or 313 nm of solutions of (Bu4N)2[ReBr6] in ethyl bromide exposed to air causes complete conversion of the hexabromorhenate(IV) to perrhenate ion. The rate of the reaction is linearly dependent on the incident light intensity and on a combination of the fraction of light absorbed by the rhenium complex and the fraction absorbed by the ethyl bromide. The experimental results are consistent with a mechanism in which the peroxy radical CH3CH(Br)OO, produced in both the solvent-initiated and metal-initiated pathways, oxidizes [ReBr6]2− by electron transfer.