Selective removal of NOx by binary oxide systems of Ba-Cu and Mn-Zr was investigated. These mixed oxides were effective in removing NOx at 400℃ by absorption in or on the solid as nitrate. The reaction was investigated by oxidation of NO which was promoted in the presence of O₂ on Mn or Cu sites. Then, the oxidized species were stored in the solid as nitrate ions on Ba or Zr sites. The amorphous phase of the Mn-Zr oxide which was prepared by heating the coprecipitation at 450℃ for 5hr was effective for NOx removal. The surface areas of Ba-Cu and Mn-Zr oxide were 0.20m²/g and 177.80m²/g, respectively. Mesopore whose pore size was ca. 46.20Å was observed in the Mn-Zr oxide sample. Although the NOx absorption was hindered by coexisting CO₂ for the Ba-Cu oxide system, the absorption in the Mn-Zr oixde was hardly affected by CO₂ and was enhanced with increasing O₂ concentration. The Ba-Cu oxide absorbed ca. 0.59 mol/mol Ba.