The reaction of alkenes with N-bromosuccinimide and triethylamine tris(hydrofluoride) produces vic-bromofluoroalkanes (1) with high yields. As long as the addition to the double bond is sterically unhindered, bromine and fluorine get attached with very high regioselectivity, the latter halogen occupying the more substituted, carbocation stabilizing position. 2-Fluoro-1-alkenes give 1-bromo-2,2-di-fluoroalkanes