The Data File Documentation reports on the procedures and methodologies employed during the Education Longitudinal Study of 2002 base year, first, and second follow-ups, with special emphasis on the second follow-up (2006). The document is designed to provide guidance for users of the restricted-use data as released in Electronic Codebook (ECB) format (NCES 2008-346) and also contains information that will be valuable to users of the public-use Data Analysis System (DAS). Included in the documentation are the following: an overview of the study and its predecessor studies; an account of instrumentation and high school records (academic transcript) collection; documentation of the sample design, weighting, imputation, and design effects; a summary of the data collection methodology and results, including detailed response rates; a description of data preparation and processing activities including linkage to ancillary external data sets and creation of composite variables; and an overview of data file structure and contents. The following are appended: (1) Cross-Cohort Comparisons; (2) Quick Guide to Using the ELS:2002/06 Data; (3) Synopsis of the ELS:2002 Second Follow-up Field Test Report; (4) Data File Documentation Errata; (5) Flow Chart and Facsimile for the Second Follow-up Questionnaire; (6) Occupational Coding Crosswalk; (7) Transcript Standard Errors and Design Effects; (8) Propensity Models Versus Weighting Cell Approaches to Nonresponse Adjustment: A Methodological Comparison; (9) Average Weight Adjustment Factors; (10) Standard Errors and Design Effects; (11) Nonresponse Bias Tables; (12) Variable List for the ELS:2002 Electronic Codebook (ECB) and Data Analysis System (DAS); (13) Second Follow-up Composite Variables; (14) Data Imported Into ELS:2002 From External Sources; and (15) Glossary of Terms. (Individual appendices contain references.) [For "Education Longitudinal Study of 2002: Base-Year to First Follow-Up Data File Documentation. NCES 2006-344," see ED489083.]