High‐repetition‐rate (500 pps) laser action in XeF molecules at 351 and 353 nm in a gas mixture of He, Xe, and NF3has been demonstrated by use of a blowdown‐type fast‐flow system and thyratron‐switched high‐repetition‐rate pulse generators. The transverse‐flow velocity was 14 m/sec across a discharge region of 1×0.4×30 cm at a pressure of 650 Torr. The electric discharge pulse width was 60 nsec. For single‐shot operation, laser output energy of 6 mJ/pulse and electric efficiency of 0.25% have been obtained. For high‐repetition‐rate operation, the output energy per pulse was only 3 mJ as a result of the long charging time constant.