To support and promote secondary analyses, the International Association for the Evaluation of Educational Achievement (IEA) is making the SITES 2006 international database and accompanying User Guide available to researchers, analysts, and public users. The database comprises national contexts and school- and teacher-level data from 23 education systems, all of which gave IEA permission to release their national data. It includes information from roughly 8,000 schools, including more than 13,000 mathematics and over 16,000 science teachers. The SITES 2006 User Guide describes the content, format, and usage of the SITES 2006 international database. Chapter 2 describes the structure of the database in detail including information about the response, sampling, and derived variables and their coding. Chapter 3 details the weighting and variance estimation methods used in SITES 2006 and provides information on the use of weights and guidelines for estimating variance when conducting secondary analysis. Chapter 4 provides instructions on analyzing the SITES 2006 international database using IEA's International Database (IDB) Analyzer software to replicate the results presented in the SITES 2006 international report as well as to conduct secondary analysis. Appendices include: (1) SITES 2006 National Context Questionnaire; (2) SITES 2006 Principal Questionnaire; (3) SITES 2006 Technical Questionnaire; (4) SITES 2006 Teacher Questionnaire; and (5) Characteristics of the Australian Sample. (Contains 6 footnotes, 4 tables, and 24 figures.) [Contributors include: Eugenio J. Gonzalez; Juliane Hencke; and Olaf Zuehlke. For the "SITES 2006 Technical Report," see ED510137.]