Application of thermal dissociation of O2, developed within arc-heated gas mixtures, followed by a sufficiently rapid convection to preserve O atom concentrations and subsequent CS2 injection, has generated efficiently a CO laser medium. In preliminary experiments, this pumping technique has produced a 34-W cw laser emitting over a band of vibration-rotation transitions from 4.9 to 5.7 μ from a 5-cm active transverse optical cavity.