After the Wenchuan earthquake,The Institute of Engineering Mechanics (IEM) performed an extensive and comprehensive damage survey of the large area affected by the earthquake. Seismic codes in China were revised and updated after the catastrophic 1976 Tangshan earthquake. However,until the Wenchuan earthquake the seismic code provisions were not tested by a large earthquake. Some 5000 buildings,exposed to intensities VI to XI,were investigated in great detail immediately after the earthquake. The investigation and the surveys covered both seismically designed (fortified) buildings and non-code compliant buildings. In the process a comprehensive and documented database of building performance was compiled,which would be very valuable for further research,improvement of the seismic code,improvement of the construction practices,and disaster mitigation planning and management. The database dominantly contains the most prevalent structural types in the region: 1) reinforced and un-reinforced masonry structures; 2) masonry buildings with reinforced frame in the lower stories,and 3) reinforced concrete frame structures. Observed damage characteristics of various structural types were studied and documented,damage patterns analyzed,and corresponding damage probability matrices derived from the data collected during this survey. It is our hope that this investigation and the published material will be utilized for the revision of the seismic codes,leading to a higher level of life safety and damage reduction in future earthquakes. After the Wenchuan earthquake, The Institute of Engineering Mechanics (IEM) performed an extensive and comprehensive damage survey of the large area affected by the earthquake. Seismic codes in China were revised and updated after the catastrophic 1976 Tangshan earthquake. However, until the Wenchuan earthquake the investigation of the earthquake code provisions were not tested by a large earthquake. Some 5000 buildings, exposed to intensities VI to XI, were investigated in great detail immediately after the earthquake. compliant buildings. In the process a comprehensive and documented database of building performance was compiled, which would be very valuable for further research, improvement of the seismic code, improvement of the construction practices, and disaster mitigation planning and management. The database dominantly contains the the most prevalent structural types in the region: 1) reinforced and un-reinforc ed masonry structures; 2) masonry buildings with reinforced frame in the lower stories, and 3) reinforced concrete frame structures. Observed damage characteristics of various structural types were studied and documented, damage patterns analyzed, and corresponding damage probability matrices derived from the data collected during this survey. It is our hope that this investigation and the published material will be utilized for the revision of the seismic codes, leading to a higher level of life safety and damage reduction in the future earthquakes.