The electrical conductivity of molten K(3)AIF(6), Rb(3)AIF(6), Cs(3)AIF(6), and CsF was measured at various temperatures using a pyrolytic boron nitride tube, platinum-rhodium alloy electrode, and alternating current impedance method. The electrical conductivity of molten K(3)AIF(6) was found to be 2.64 S.cm(-1) at 1273 K The electrical conductivity of molten Rb(3)AIF(6) was found to be 2.06 S.cm(-1) at 1273 K. The conductivity of molten Cs(3)AIF(6) at the same temperature is 1.36 S-cm(-1) because the conductivity of CsF at 1273 K was found to be 2.57 S.cm(-1). The electrical conductivity values steadily drop from lithium fluoride/fluoroaluminate through sodium and potassium to cesium fluoride/fluoroaluminate. This fall in conductivity is probably because of the increase in the size and mass of the cations (activation energy increases with decreasing conductivity).