Substance use is a leading cause of preventable morbidity and mortality, and is in large part why people in the U.S. have the highest probability among industrialized nations of dying by age 50. Substance use deserves our sustained attention. It is also an important determinant of many social ills including child and spouse abuse, violence more generally, theft, suicide, and more; and it often begins in adolescence. Monitoring the Future (MTF) is designed to give sustained attention to substance use among the Nation's youth and adults. It is an investigator-initiated study that originated with and is conducted by a team of research professors at the University of Michigan's Institute for Social Research. Since its onset in 1975, it has been continuously funded by the National Institute on Drug Abuse--one of the National Institutes of Health--under a series of peer-reviewed, competitive research grants. The 2013 survey, reported here, is the 39th consecutive survey of drug use and related attitudes and beliefs among American high school seniors, the 34th such survey of American college students, and the 23rd such survey of 8th- and 10th-grade students. Importantly, results are also reported for high school graduates followed in a series of panel studies through age 55. Two of the major topics included in the present volume are (1) the "prevalence and frequency" of use of a great many drugs among American secondary school students in 8th, 10th, and 12th grades and (2) "historical trends" in use by students in those grades. Distinctions are made among important demographic subgroups in these populations based on gender, college plans, region of the country, population density, parent education, and race/ethnicity. MTF has demonstrated that key attitudes and beliefs about drug use are important determinants of usage trends, in particular the amount of risk to the user perceived to be associated with the various drugs and disapproval of using them; thus, those measures also are tracked over time, as are students' perceptions of certain relevant aspects of the social environment--in particular, perceived availability, peer norms, use by friends, and exposure to use by others of the various drugs. Data on grade of first use, discontinuation of use, trends in use in lower grades, and intensity of use are also reported. Appendices are included. [For "Monitoring the Future National Survey Results on Drug Use, 1975-2013. Volume 2, College Students & Adults Ages 19-55," see ED578547.]