The nitrogen-sensing properties of LaAl12O18N are described for the first time. Positive e.m.f. measurements at high temperature across the cells alpha-Nb (N), beta-Nb2N, alpha-Al2O3, LaAl12O18N LaAl11O18 (or LaAl12O18N) LaAl12O18N, alpha-Al2O3, beta-Nb2N, gamma-Nb4N3, were in agreement with P-N2 (beta-Nb2N, gamma-Nb4N3) > P-N2(alpha-Nb(N), beta-Nb2N) for the idealized stoichiometric cell reaction gamma-Nb4N3 + 2 alpha-Nb(N) --> 3 beta-Nb2N, thus demonstrating the nitrogen-sensing property of these cells. The e.m.f. for a variety of cells with electrodes containing beta-V2N, beta-Nb2N, beta-Ta2N and "Ti2N", were consistent with the predicted equilibrium nitrogen partial pressures.