The effectiveness of alkali carbonate-treated and alkali hydroxide-treated gamma-alumina for the adsorption of NO2 and NO has been examined in this study. All of the alkali-treated aluminas perform better than bare aluminas, and the performance of the alkali-treated aluminas improves with increasing mass (atomic radii) of the alkali. The most efficient material examined is 33% CsOH-treated gamma-alumina. As NO2 is adsorbed, NO is produced in a 3:1 ratio. Surface acidity does not affect the adsorption of these species. The adsorbed N-containing species are strongly bound at the sorbent surface with a decomposition temperature over 600 degrees C. Thermal desorption of these species provides an effective means of regenerating these materials.