The title of this document, FEMA 356 Prestandard and Commentary for the Seismic Rehabilitation of Buildings, incorporates a word that not all users may be familiar with. That word-prestandard-has a special meaning within the ASCE Standards Program in that it signifies the document has been accepted for use as the start of the formal standard development process, however, the document has yet to be fully processed as a voluntary consensus standard. The preparation of this prestandard was originally undertaken with two principal and complementary objectives. The first was to encourage the wider application of the NEHRP Guidelines for the Seismic Rehabilitation of Buildings, FEMA 273, by converting it into mandatory language. Design professionals and building officials thus would have at their disposal a more specific reference document for making buildings more resistant to earthquakes. This volume fully meets this first objective. The second objective was to provide a basis for a nationally recognized, ANSI-approved standard that would further help in disseminating and incorporating the approaches and technology of the prestandard into the mainstream of design and construction practices in the United States. How successfully this volume achieves the second objective will become apparent with the passage of time, as this prestandard goes through the balloting process of the American Society of Civil Engineers. Several additional related efforts were ongoing during the development of this prestandard. A concerted effort was made to gather any new information produced by these endeavors. Topics varied considerably, but typically covered approaches, methodologies, and criteria. Whenever an analysis of the new information disclosed significant advances or improvements in the state-of-the-practice, they were included in this volume. Thus, maintaining FEMA 273 as a living document-a process to which FEMA is strongly committed-is continuing.