A XeCl longitudinal–discharge laser is analyzed which operates at low pressure with UV preionization in different buffer gases (He, Ne, and Ar). Its output energy reaches 0.1 mJ at a pulse length of 5 ns and a total pressure of the gas mixture of 45 mm Hg. The XeCl laser has also operated without buffer gas, at E/P = 100 V/cm*mm Hg.