The output energy and pulse shape of XeF/KrF lasers pumped by fast discharges were measured at various gas compositions and total pressures. For the KrF laser, the maximum output (1.6 mJ) was obtained in a gas mixture of He:Kr:NF3=100:5:0.2 at a total pressure of 700 Torr. The output energy density was 160 mJ/l, and the electrical efficiency was 0.06%. The peak power was 55 kW. For the XeF laser, the maximum output (10 mJ) was obtained in a gas mixture of He:Xe:NF3=100:4:2 at a total pressure of 500 Torr. The peak output power was 1 MW. The output energy density (660 mJ/l) was a factor of 10 higher, and the efficiency (0.5%) was a factor of 2.5 higher than reported earlier.