Microwave excitation of laser gases allows the deposition of high excitation energy densities into an active medium of relatively large diameter and volume. To take advantage of low cost commercially available generators a microwave frequency of (upsilon) equals 2.45 GHz was chosen. An oscillator amplifier system with TEM00 beam quality and tunable wavelength is used in order to obtain a cw laser output of maximum PL equals 7 kW. The output of a dc discharged, diffusion cooled CO2 laser oscillator operating in the TEM00 mode with an output power of 265 W (cw) and an average power of maximum 140 W in the pulsed mode is fed into an amplifier consisting of 24 modules, excited by two magnetrons of 2.7 kW power each. The discharge diameter of an amplifier module is d equals 0.051 m and the active length for one discharge module is 1 equals 0.3 m, yielding an active gain path of Lakt equals 7.2 m. In the pulsed mode the amplifier delivers a peak power of up to 1.9 MW at a repetition rate of 10 kHz.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.