A solid-electrolyte gas sensor for the detection of NO gas has been constructed using a novel nitrite sodalite material as the solid electrolyte. The following galvanic cell is assembled and e.m.f. measurements taken: Ag|AgNa(AlSiO)(NO )|Au,NO. A linear dependence of the sensor's e.m.f. response on ln P is observed. The dependence of the sensor's e.m.f. and response rate on operation temperature has been studied. The e.m.f. of the nitrite sodalite-based sensor is found to be independent of oxygen partial pressure. A one-electron electrode process is proposed for the sensor.