A pulsed chemical laser using the reaction between fluorine and hydrogen or deuterium is described. The reactants are mixed at a pressure which is above the second explosion limit, and reaction is initiated by photolytic dissociation of the fluorine. Laser pulse energies of 96 mJ were achieved from hydrogen fluoride, and 350 mJ from carbon dioxide which acquires vibrational energy by transfer from deuterium fluoride. These pulse energies are lower than expected theoretically.