The homogeneous catalytic removal of NO and SO2 with the hexamminecoblt(II) (Co(NH3)(6)(2+) solution is a novel alternative to comply with the environmental emission standards. The mass transfer and kinetics of the absorption of NO and SO2 into the aqueous Co(NH3)(6)(2+) solutions have been investigated in a double-stirred reactor. The experimental results indicate that the gas-liquid reaction between NO and Co(NH3)(6)(2+) with 5.2% oxygen coexisting in the gas phase becomes gas film controlling as Co(NH3)(6)(2+) concentration exceeds 0.03 mol l(-1) when there is 1600 ppm SO2 in the gas phase. NO absorption rate is proportional to its inlet concentration. Higher SO2 concentration in the gas phase reduces the NO absorption rate into the Co(NH3)(6)(2+) solution. The NO absorption rate decreases with temperature as it is above 34 degrees C and the disadvantage of temperature is smaller in the presence of SO2 than in the absence of SO2. Oxygen in the gas phase is of benefit to the NO absorption. A high oxygen partial pressure is more beneficial to the combined removal of NO and SO2 with the Co(NH3)(6)(2+) solution. The NO absorption rate increases with pH of the Co(NH3)(6)(2+) solution. A high pH is especially favorable to the combined removal of NO and SO2. A kinetic equation for NO absorption under gas film controlling at 50 degrees C has been obtained as