Stimulated emission on theP(43) andR(70) transitions of the BiF (A‐X,v’=1 tov‘=4) band was demonstrated, using the reaction of premixed FN3and Bi(CH3)3. The transient chemistry was thermally initiated by a pulsed CO2laser, using SF6as a sensitizer, while amplification was detected using an e´talon‐tuned pulsed dye laser probe and a sensitive cavity ringdown technique. The magnitude of the peak gain, estimated at 3.6×10−4/cm, was consistent with a negligible concentration of the terminal BiF(X,v‘=4) state, based on the calculated optical cross section and the peak concentration of the BiF (A,v’=1) state, as measured by absolute photometry.