Detailed performance characteristics of a closed‐cycle subsonic cw CO laser excited by a transverse self‐sustained dc glow discharge are described. Using an electrode configuration which consists of a hollow‐type cathode and a planar anode, the discharge characteristics have been measured under various gas conditions. The measurements show that the discharge instability, and hence the available discharge input, are strongly influenced not only by gas temperature and total static pressure but also by gas composition. From a discharge volume of about 480 cm3, a laser output power of 406 W is extracted with an electrical conversion efficiency of 11.6% for a mixture of CO/N2/He/O2=6/16/78/0.19 at an entrance gas temperature of 156 K. Furthermore, by applying an additional cathode array, the discharge uniformity and the specific input energy have been enhanced. As a result, the maximum extracted laser output reaches as high as 729 W or 1820 W per m of discharge length, with the corresponding conversion efficiency and specific output energy of 16.3% and 125 J/g, respectively. This performance is comparable to or higher than that which has been obtained with an electron‐beam controlled discharge, a pulser‐sustained discharge, etc.