Laser emission from vibrationally excited CO (CO†) has been observed when mixtures of CSe2, O2, and He are partially dissociated by a pulsed electric discharge. Observations on the spontaneous emission confirm that the CO†is formed in the reaction O + CSe → CO†+Se, which is 118 kcal/mole exothermic and produces CO selectively in high vibrational levels. A comparison is made with the analogous system O + CS → CO†+S.