A summary of the experimental fatigue characterization of FRP composite bridge decks at two extreme temperatures [-30 ° C (-22 ° F) and 50 ° C (122 ° F)] is presented. Each deck was initially subjected to one million wheel load cycles at low temperature and another one million cycles at high temperature [1,2]. The results presented in this paper correspond to the fatigue response of each deck for four million load cycles at low temperature and another four million cycles at high temperature. Thus, the each deck was subjected to a total of ten million cycles. Progressive degradation in stiffness with cycling was noted for each deck. Comparisons of responses were made between the different FRP composite deck configurations and materials.