Pulsed HF and DF chemical lasing has been observed in SF6:F2:H2and SF6:F2:D2mixtures, respectively, using an electron beam to initiate the laser reactions. Maximum pulse energies of 50 J with peak output power of 50 MW and an electrical efficiency of 6% were obtained with a 4195‐cm3active volume, a total pressure of 240 Torr, and gas component ratios SF6:H2:F2of 1.33:1.0:1.0. For an active volume of 236 cm3, a total pressure of 420 Torr, and SF6:H2:F2equal to 1.5:1.0:1.0, 11 J energy was obtained corresponding to an energy density of 80 J/l atm. For DF lasing from mixtures of SF6, D2, and F2, the output energy is a factor of 2–3 smaller than for HF lasing from mixtures of SF6, H2, and F2with the same initial conditions.