Seismic response of bridges with sliding isolation system between sLiperstructure and substructure is investigated. Frictional force of the isolation system is assumed to have ideal Coulomb-friction characteristics. In addition, a linear restoring force is also provided by the isolation system. The governing equations of motion of the isolated bridge system are derived. Seismic response of the isolated bridge system in both longitudinal and transverse directions is obtained by solving the non-linear equations of motion (non-linearity due to sliding system) in the incremental form using Newmark’s method. The system is subjected to real earthquake ground motion (i.e. EI-Centro 1940) in both horizontal directions. In order to study the effectiveness of the isolation devices, the seismic response of the isolated bridge is compared with the corresponding response of non-isolated bridge (i.e. bridge without isolation devices). In addition, a parametric study is conducted to investigate the effectiveness of sliding system for aseismic design of the bridges with different combinations of the superstructures and the piers. It is shown that the sliding system is quite effective in reducing the seismic response of bridges.