The copper-mediated trifluoromethylation of alkyl radicals is described. The combination of Et3SiH and K2S2O8 initiates the radical reactions of alkyl bromides or iodides with BPyCu(CF3)(3) (BPy = 2,2'-bipyridine) in aqueous acetone at room temperature to afford the corresponding trifluoromethylation products in good yield. The protocol is applicable to various primary and secondary alkyl halides and exhibits-wide functional group compatibility. A mechanism involving trifluoromethyl group transfer from Cu(II)-CF3 intermediates to alkyl radicals is proposed.