Simultaneous absorption of NO₂ and NO into alkaline solutions was studied in a wide range of gaseous concentrations, NO₂ from 5 to 2000 ppm and NO from 0.066 to 1.2%. The absorption rate was not dependent on the concentration of hydroxide ion in the solution, if the alkalinity in the vicinity of the interface was maintained. In the presence of NO in excess of NO₂, the stoichiometry of the absorption is expressed by the reaction NO+NO₂+2OH^-→2NO₂^-+H₂O and the rate is proportional to the product of the interfacial concentrations of NO₂ and NO. The predominant mechanism is considered to be the solution of N₂O₃ in equilibrium with NO and NO₂ at the interface followed by its rapid hydration. The absorption rate is expressed by H√k₂D [N₂O₃]G, H√k₂D being 2.55 m•s^-1, which is about two orders of magnitude greater than the corresponding value for the absorption of N₂O₄.