Severe damage is caused to property by earthquakes, especially to necessitate architects and manmade structures. Seismic isolation is the better solution as many researchers studied and reviewed for the earthquake resistant design of the structures. This is because base isolation confines the effects of the earthquake strike, a workable base isolating structure largely separating the structure from the ground motion, and the isolated structural counter accelerations are usually less as compared to the regular structural counter acceleration in response to ground acceleration. The present work is intended to provide a systematic procedure to assess the behavior of a structure during the seismic excitation. In this work, a lead rubber bearing isolator is used to high-rise RC buildings by doing Response Spectrum Analysis using ETABS software. The fundamental goal of base isolation is to reduce substantially the absorption of the earthquake-induced force and energy by the structure. Base isolation system significantly reduces the superstructure lateral stiffness and ductility compared to the un-isolated structure which is demonstrated by the results of this work. This allows cost saving from less material being spend on lateral system and implication of structural detailing