Traditional glassy ion conductors exhibit Arrhenius temperature dependence of the d.c. conductivity. Recently, Kinc and Martin1 reported the discovery of a Fast Ion Conducting (FIC) glass with ionic conductivities as high as 10-2 (O-cm)-1. Surprisingly, while this is a very high conductivity for a glassy material, it is still several orders of magnitude lower than that predicted by the low temperature Arrhenius behavior. While Kinc and Martin did a through investigation of these materials at low temperatures, they did not explore the room temperature and above behavior. They proposed a simple model to explain their observed non-Arrhenius ionic conductivity, but the full study of the behavior was not been made.;Several researchers have since attempted to explain the cause of the behavior observed by Kinc and Martin; however, no conclusive evidence has been given for the true origin of this behavior. Most of the models have been purely mathematical fits, with no basis in the physical world. Other researchers simply write off the observed behavior as a fluke of crystallized or phase separated samples. The present investigation looks at the high temperature behavior of the same glass compositions that Kinc and Martin looked at to determine if there is ionic conductivity saturation or perhaps even an ionic conductivity maximum. This work goes on to develop a theory that explains the observed results in a physical manner that is based on current knowledge ionic conductors and glass structure.;1Kincs, J., Martin, S. W., Phys. Rev. Let., 76, 70--73