Now in its 32nd year, the study is comprised of several ongoing series of annual surveys of nationally representative samples of 8th- and 10th-grade students (begun in 1991), 12th-grade students (begun in 1975), and adults (begun in 1976). As we report in this volume, several segments of the adult population are covered in the follow-up surveys of high school graduates. One important segment is American college students; a second is their age peers who are not attending college, sometimes called the forgotten half; and a third is all young adult high school graduates of modal ages 19 to 30, which we refer to as the young adult sample. Finally, high school graduates at the specific modal ages of 35, 40, and 45 are included each year in longer term follow-ups. The follow-up surveys have been conducted by mail on representative subsamples of the previous participants from each high school senior class. The present volume presents data from the 1977 through 2006 follow-up surveys of the graduating high school classes of 1976 through 2005 as these respondents have progressed into adulthood - now through age 45 for the oldest respondents, and soon to be through age 50. The college student population comprises all full-time students, one to four years post-high school, enrolled in a two- or four-year college in March during the year of the survey. More is said about this sample definition in chapters 3 and 8. Results on the prevalence of drug use among college students and their noncollege peers in 2006 are reported in chapter 8, and results on the trends in substance use among college students and their noncollege peers over the past 27 national surveys are reported in chapter 9. (Extract of the publication)