The rate constant k for the gas-phase reaction of atomic hydrogen with 1,1,2,3,4,4-hexafluoro-1,3-butadiene has been measured over the temperature range 290-1010 K by time-resolved atomic resonance fluorescence using H 2 O and NH 3 as precursors, at argon pressures of about 30-140 mbar. Over the range 290-620 K a positive activation energy was observed, k ) (3.40 ( 0.34) × 10 -11 exp[(-16.7 ( 0.4) kJ mol -1