A computer model of the unstable‐resonator CO electric‐discharge laser is presented. The molecular kinetics model treats CO/Ar/He mixtures and includes the processes of VV and VT energy transfer, spontaneous and stimulated emission, electron collisions of the first and second kind, and one‐dimensional gas flow with heat addition. Optical propagation in the unstable resonator is treated with diffractive calculations based on the Fast Fourier Transform. An assumed initial field distribution is propagated back and forth between the mirrors of the resonator and allowed to interact with the laser medium according to a thin‐sheet gain model. These propagations are continued until successive ones yield nearly identical values for intensities, saturated gains, temperature, etc. These are the values predicted for the laser operating under the assumed conditions. The results of sample calculations are presented and discussed.