A computer model of a CO chemical laser produced by supersonic mixing of CS/S with O2is presented. The model has been shown to accurately predict measured gain coefficients of P7(14) and P5(18) lines, hence it was utilized for further parametric studies leading to a better understanding of the processes involved in laser operation. The model predicts high gain and high specific available energy inv= 1→0 tov= 20→19 transitions. A maximum gain was obtained for each of the parameters investigated. For certain operational conditions, complete population inversion was observed.