Laser action at 172.9 nm has been observed in xenon and krypton‐xenon mixtures following short‐pulse excitation (2.5 nsec) by a relativistic electron beam. Peak powers [inverted lazy s] 80 kW cm−2in a 5‐nsec pulse were obtained. The pumping sheme used in this work is noteworthy because its high efficiency has made it possible to utilize a simple compact electron accelerator (total electron beam energy 6 J) for excitation. The present short‐pulse data suggest that the rapid decrease in energy efficiency of this laser at high xenon pressures may be due to excited‐state quenching by ground‐state xenon atoms.