The Aegean is one of the most seismically active regions of Turkey. The Eqarthquake disasters which occurred in Turkey recently, obligate the seismic rehabilitation of existing buildings and the new construction projects produced to require well-detailed seismic strengthing. On the other hand, before starting an expensive project such as seismic rehabilitation, a benefit/cost analysis is needed to determine whether the proposed project is economically feasible. In this study, a benefit/cost analysis model for the seismic rehabilitation of existing reinforced concrete buildings in Izmir is presented. To express the seismicity of Izmir City, between 1900-2003, the magnitude of Ms 4.9 earthquakes which occurred in Izmir and its vicinity are used as data. The Poisson Model is used to calculate the probability of occurrence. For the seismic risk of Izmir which includes damage to buildings and loss, various damage estimation methods are described. As a generalization of all of the existing reinforced concrete buildings in Izmir Region, two existing reinforced concrete buildings with total building area of 735 square meters and 716 square meters, respectively, which have different social functions, are chosen to estimate whether the seismic rehabilitations of the investigated buildings are economically justified. As a result of the analysis, benefit/cost ratios of both structures are found greater than one which means both rehabilitation projects are economically feasible.