The dielectric constants of benzaldazine (BA) and its nitro derivatives have been measured at different frequencies up to 200 kHz. The measurements were carried out at temperatures up to and near the melting point of each sample. Two phase transitions were obtained during measurements at 310 and 480 K. Inversion -NN- rotation and inversion -CN- rotation mechanisms may be responsible for these transitions. The effect of interaction between the strongly polar -NO2 group of o-, m- or p-nitrobenzaldazine and the central aldimino (-CH=N-) groups on the dielectric constant is discussed. The electric dipole moments of the samples were calculated at the peak positions, and are discussed.