This volume - the second in a two-volume set from the Monitoring the Future study - provides findings on the substance use and related behaviors of several segments of the adult population. It also contains findings on attitudes and beliefs about drugs, as well as on several particularly salient dimensions of their social environments. Volume I presents similar findings for American secondary students in grades 8, 10, and 12. One important segment covered here is the population of American college students; a second is their age peers who are not attending college. Also covered in this volume are young adult high school graduates ages 19 to 30 (including the college students), as well as high school graduates at ages 35, 40, and 45. Monitoring the Future is a long-term research program conducted at the University of Michigans Institute for Social Research under a series of investigator-initiated research grants from the National Institute on Drug Abuse. Now in its 30th year, it comprises, in part, ongoing series of annual nationally representative surveys of 12th (begun in 1975) and of 8th- and 10th-grade students (begun in 1991). Over the years, follow-up surveys have been conducted of representative samples of the previous participants from each high school senior class. The present volume presents data from the 1977 through 2004 follow-up surveys of the graduating high school classes of 1976 through 2003 as these respondents have progressed into adulthood - through age 45 for the oldest respondents. To permit this volume to stand alone, we have repeated some material from Volume I. Specifically, chapter 2 in this volume is the same as chapter 2 in Volume I; it provides an integrated overview of the key findings presented in both volumes. Chapter 3, Study Design and Procedures, is also the same as chapter 3, Volume I. The reader already familiar with Volume I may wish to skip over these chapters. Otherwise, the content of the two volumes does not overlap. (Extract)