A computer simulation of a pulsed HF laser pumped by the H(2) + F(2) chain reaction is presented. A chemical kinetic model encompassing sixty-eight reactions is used to approximate the reacting mixture contained within an optical cavity. For each vibrational level, a Boltzmann distribution for the rotational levels is assumed, with lasing on the vibrational band at line center of the transition having maximum gain. An analysis of cavity and chemical mechanisms yields a simple relationship between the pumping and depletion rates of the vibrational levels. This relationship is used to make a comprehensive study of the effects of cavity and chemical parameters on the laser pulse. The effect of changes in uncertain chemical reaction rate coefficients is assessed. A competition exists between vibrationtranslation deactivation reactions and stimulated emission. Laser performance is most sensitive to the relative rates of the vibrational-translational and pumping reactions. In addition, the effect of the photon flux on the chemical mechanisms is significant.