Fragility curves are functions which represent the probability that a given structure’s response to various seismic (conditions) excitations exceeds performance limit states. As such, fragility curves are a measure of performance in probabilistic terms. The major objectives of MCEER research on fragility information are: (1) developing efficient and accurate methods to calculate fragility curves for structural and nonstructural components and for global assemblies (systems); (2) establishing fragility information as a base for performance-based design, cost and loss assessment, and decision policies; (3) developing optimal strategies for seismic rehabilitation based on cost-benefit analysis; and (4) establishing rational performance limit states based on interaction between engineering and socioeconomic issues.