The present paper deals with a model for obtaining the optimum performance conditions for the KrF laser. The model is based on the dominant formation, quenching and absorption processes. For a given excitation density the analysis predicts the maximum photon density rate that can be extracted from the cavity together with the corresponding optimum argon and krypton densities as a function of the excitation rate and outcoupling. The results of various experimental studies indicated in the paper are in good agreement with these predictions. The analysis shows that the maximum efficiency that corresponds with the maximum output defined as the ratio of output power and the ionization energy delivered to argon is about 8%.