The "2004/06 Beginning Postsecondary Students Longitudinal Study (BPS:04/06)" is sponsored by the U.S. Department of Education to respond to the need for a national, comprehensive database concerning issues students may face in enrollment, persistence, progress, and attainment in postsecondary education and in consequent early rates of return to society. The BPS Longitudinal Study follows the paths of first-time beginners (FTBs) for a number of years as they navigate the system of postsecondary education, and captures transfer patterns, co-enrollment, and periods of nonenrollment (stopouts). The BPS Longitudinal Study is unique in that the FTB cohort is tracked regardless of when they completed high school or how many colleges they attend. Students are classified as FTBs during the base-year survey of the 2003-04 National Postsecondary Student Aid Study (NPSAS:04), and tracked from that point forward. This report describes and evaluates the methods and procedures used in the "2004/06 Beginning Postsecondary Students Longitudinal Study (BPS:04/06)," the first follow-up of the cohort of first-time beginning students who were identified as part of the 2003-04 National Postsecondary Student Aid Study (NPSAS:04). The introductory chapter describes the background, purpose, schedule, and products of BPS:04/06. Chapter 2 describes study design and procedures. Chapter 3 presents data collection outcomes, while chapter 4 presents evaluations of the quality of the data collected. Chapter 5 reviews the data file development process. Finally, chapter 6 describes the weighting and variance estimation procedures and reports on the quality of the estimates. Further information about the study, including members of the Technical Review Panel, data elements, instrument facsimile, materials used during interviewer training and data collection, and additional technical details about the data, are provided as appendixes to the report and cited in the text where appropriate. (Contains 47 tables and 8 figures.).