A recently implemented advanced seismic monitoring system for a 24-story building facilitates recording of accelerations and computing displacements and drift ratios in near-real time to measure the earthquake performance of the building. The drift ratio is related to the damage condition of the specific building. This system meets the owner's needs for rapid quantitative input to assessments and decisions on post-earthquake occupancy. The system is now successfully working and, in absence of strong shaking to date, is producing low-amplitude data in real time for routine analyses and assessment. Studies of such data to date indicate that the configured monitoring system with its building specific software can be a useful tool in rapid assessment of buildings and other structures following an earthquake. Such systems can be used for health monitoring of a building, for assessing performance-based design and analyses procedures, for long-term assessment of structural characteristics, and for long-term damage detection.