Abstract: The seismic response of bridges seismically isolated by elastomeric bearings to earthquake excitation is presented in this paper. The specific objective of the study is to identify the various parameters affecting the response of the isolated bridge and to assess the effects of seismic isolation on peak responses of the bridge. The seismic response of the lumped mass model of continuous span isolated bridges is obtained by solving the governing equations of motion in the state space form. To study the effectiveness of bearings, the seismic response of isolated bridges subjected to various near field and far field earthquakes is compared with the response of corresponding non isolated bridges (i.e. bridges without isolation devices). The specific objectives of the study are to investigate the performance of bridge isolated by LRB and to investigate the optimum parameters of the LRB bearing for minimum earthquake response of the isolated bridge under different near field and far field earthquake ground motions.