The Text REtrieval Conference (TREC) is sponsored by three agencies—the U.S. National Institute of Standards and Technology (NIST), the U.S. Department of Defense, Advanced Research Projects Agency (DARPA), and the U.S. intelligence community’s Advanced Research and Development Activity (ARDA)—to promote text retrieval research based on large test collections. Overviews of TREC (Harman & Voorhees, 2006; Voorhees & Harman, 2005) and the TREC Web site (trec.nist. gov) have provided a comprehensive review of TREC conferences. This section is compiled based on these resources. TREC started in 1992 with 25 participating groups, including the leading text retrieval groups, to search two gigabytes of text. For each TREC, NIST offers a test collection and questions. Participating teams follow the guidelines, run the data on their own IR systems, and return the results to NIST. NIST evaluates the submitted results and organizes workshops for participants to discuss their experience and present results. By the end of 2005, 14 TREC conferences had been held.