The results are reported of a theoretical study on the pulsed HBr chemical laser using a mixture of H2and Br2, utilizing numerical analysis by pulsed chemical‐laser code. The HBr laser output performance as characterized by laser energy, power, pulse width, and vibrational population distribution was examined as a function of the initial dissociation rate and the H2/Br2mixture ratio for a mixture at 100 Torr. The effect of HBr(0) in an HBr chemical laser must be taken into account, especially in applying HBr chemical lasers to the optical pumping of CO2and HBr gases, since the 4.2‐&mgr;m laser emission useful for such pumping comes from theP1−0(J) andP2−1(J) lines. In this paper, the effect of added HBr(0) on output performance was also studied.