Monitoring the Future (MTF) is a long-term study of American adolescents, college students, and adults through age 50. It has been conducted annually by the University of Michigan's Institute for Social Research since its inception in 1975. It is supported under a series of investigator-initiated, competing research grants from the National Institute on Drug Abuse. The need for a study such as MTF is clear. Substance use by American young people has proven to be a rapidly changing phenomenon, requiring frequent assessments and reassessments. Since the mid-1960s, when it burgeoned in the general youth population, illicit drug use has remained a major concern for the nation. Smoking, drinking, and illicit drug use are leading causes of morbidity and mortality, both during adolescence as well as later in life. How vigorously the nation responds to teenage substance use, how accurately it identifies the emerging substance abuse problems, and how well it comes to understand the effectiveness of policy and intervention efforts largely depend on the ongoing collection of valid and reliable data. Monitoring the Future is designed to generate such data in order to provide an accurate picture of what is happening in this domain and why, and has served that function well for the past 34 years. Policy discussions in the media; in government, education, and public health institutions; and elsewhere have been informed by the ready availability of extensive and accurate information from the study relating to a large number of substances. The 2009 MTF survey encompassed over 46,000 eighth-, 10th-, and 12th-grade students in almost 400 secondary schools nationwide. The first published results are presented in this report. Recent trends in the use of licit and illicit drugs are emphasized, as well as trends in the levels of perceived risk and personal disapproval associated with each drug. This study has shown these beliefs and attitudes to be particularly important in explaining trends in use. In addition, trends in the perceived availability of each drug are presented. (Contains 17 tables and 7 footnotes.) [For the related reports, see "Volume I" (ED514370), "Volume II" (ED514367), and "HIV/AIDS: Risk & Protective Behaviors among American Young Adults" (ED514378).]