Conductivity measurements of zAgI+(1 - z)[xAg(2)S+(1 -x)(2B(2)S(3)+ 1GeS(2))] fast ion conducting (FIC) glasses were performed to explore the non-Arrhenius behavior of the conductivity above room temperature (RT). A distinct non-Arrhenius deviation is observed that causes the DC conductivity to be lower than the expected values at higher temperatures. The deviation becomes more pronounced and occurs at lower temperature as the amount of AgI is increased. A recently developed model, the ion trapping model (ITM), has been used to describe the non-Arrhenius conductivity and to fit the experimental data. It is found that the model is able to accurately reproduce the non-Arrhenius temperature dependence of the conductivity of these highly optimized fast ion conducting glasses. Under the assumptions of the model, there is only one independently adjustable parameter, the average activation energy, and it provides a physical picture of the cause of non-Arrhenius deviation. (C) 2004 Elsevier B.V. All rights reserved.