Laser gain measurements at 10.6 &mgr;m are presented for a 2.5×5×50‐cm high‐pressure uv‐sustained discharge in a CO2:N2:He:tri‐n‐propylamine gas mixture. The spatial variation of the gain, with a resolution of a 1.5‐mm‐diam spot, is discussed. The temporal behavior of the gain is shown to be influenced by the uv‐induced photoionization, an acoustical disturbance generated by the uv source arcs, and by photoemission and collisional ionization effects near the solid electrode.