A mathematical model is presented for multicomponent gas absorption with multiple reactions by, considering the ease of NOx absorption in aqueous solution of NaOH. Procedures are developed for estimating the overall reaction rates and selectivity. The effects of temperature, pressure, and NO, composition are examined Optimum design strategy is suggested by proper configuration of the oxidation and absorption stages anti by appropriate selection of levels of oxidation and absorption. A comparison between the model predictions and the performance of two operating plants is presented.