The aim of this book is to evaluate seismic performance of existing low-to-mid-rise Reinforced Concrete (RC) frame buildings. The buildings, which consist of 4, 6, 8, and 10 stories, are designed according to British standard code (BSI) and American code (ACI).Pushover analysis has been performed according to FEMA-356 guidelines;the pushover analysis is used.The lateral load patterns for pushover analysis are selected as the Regulations for earthquake resistant design of building in Egypt, 1988; these regulations have been prepared by the Egyptian Society for Earthquake Engineering (ESEE) and International Building Code (IBC 2012). Results showed that the buildings designed considering the ESEE and IBC 2012 loads were found adequate. On the other hand, the building designed according to (ESEE using BSI) satisfies the Immediate Occupancy (IO) acceptance criteria according to ATC-40.The comparison of the pushover curve shows that the stiffness of frame is larger in (ESEE using BSI)compared to the (IBC2012 using ACI) design.This means that (ESEE using BSI) design has a greater capability to resist lateral load than the (IBC2012 using ACI) design.