Three series of glasses of the Na2O-V2O5-P2O5 system corresponding to different V2O5:P2O5 ratios have been prepared and their electrical properties have been studied. Each series consisted of samples of various sodium contents. It has been found that materials of compositions xNa2O.(1-x) (0.7V2O5.0.3P2O5) and xNa2O.(1-x) (0.6V2O5.0.4P2O5) are predominantly electronic conductors. Activation energies for both series increase from 0.46 eV to 1.0 eV on increasing sodium content. The electrical conductivity at 300-degrees-C for the same range of x decreases from 1.2 X 10(-3) S/cm (for x = 0) to 1 X 10(-4)S/cm (for x = 0.5). The glasses with the lowest V2O5:P2O5 ratio (4:6) (a series xNa2O.(1-X)(0.4V2O5.0.6P2O5) for 0.3 less-than-or-equal-to x less-than-or-equal-to 0.5) exhibit mixed electronic-ionic conductivity. Activation energies for that series are in the 0. 7-0.8 eV range.