A new type of total nitrogen oxides ( NOX) gas sensor was fabricated by the conjunction of trivalent aluminum cation and divalent oxide anion conducting solid electrolytes with potassium nitrite- doped rare earth oxide- based auxiliary electrode. The sensor response was rapid, reproducible, and a continuous response was obtained. The sensor's electromotive force output is equivalent in both NO and NO2 detection with obeying the Nernst relationship, indicating that a quantitative total NOX (NO plus NO2 gases) gas detection can be successfully realized. (C) 2004 The Electrochemical Society.