On September 21, 1999 at 01:47 AM an earthquake with magnitude ML=7.3 was occurred at the central part of Taiwan. The ground shaking induced by this earthquake was felt all over the island. Near the epicenter some strong motion instruments collected ground acceleration time history with PGA greater than 980 cm/sec2. This earthquake was caused by the rupture of Chelungpu fault (the fault rupture length is about 105 kin). Because the Chelungpu fault was locate at the west coast of Taiwan and significant damage was observed. Immediately after the earthquake National Center for Research on Earthquake Engineering (NCREE) organized university professors, graduate students and practicing engineers from all over the island to investigate the damage of civil infrastructures in the earthquake affected area. The damage data collected from the reconnaissance teams was analyzed and will be used as an important documents for the study on the seismic design of structures. The reconnaissance teams included: 1.Fault and geology investigation, 2.Strong ground motion characteristics, 3.Geotechnical investigation (include: liquefaction, foundation failure, and landslide), 4.Building damage investigation, 5.Bridge and transportation damage investigation, 6.Lifeline damage investigation (include: power, communication and gas systems), 7.Industrial facility damage investigation, 8.Hydraulic system damage investigation, 9.Social and economic aspect, All the damage data collected from each reconnaissance team will provide the reconstruction and recovery committee, Executive Yuan, for their information.