The paper presents some results of experimental investigations on pumping gas lasers by an avalanche discharge sustained by UV or X-ray preionization, or by a nonavalanche discharge. Basic methods are proposed for obtaining volume avalanche self-sustained discharges of long-duration to pump XeCl, KrCl, KrF, and CO2 lasers. The conditions are determined for generating long-duration pulses connected with selecting components of buffer gas, modes of operation of UV preionization, and modes of pumping energy into the active media.