Empirical equations describing the electrical conductivities of fluorides and fluoride oxide mixtures have been obtained. These equations are based on two suppositions: (a) electrical conductivity of ionic molten substances is connected with the electronic structure of the cations; (b) the electrical conductivity of ionic melts can be expressed in terms of molar volume. In molten mixtures, the form of the electrical conductivity isotherm depends on the interaction between the components.