Monitoring the Future (MTF) study is an ongoing epidemiological and etiological research and reporting project that began in 1975. In addition to being a basic research study, MTF has become one of the nation’s most relied upon sources of information on emerging trends in illicit drug, alcohol, and tobacco use among American adolescents, college students, and young and middle-aged adults. Nationally representative samples of 8th-, 10th-, and 12th-grade students (about 16,000 in 140 schools per year per grade) will be surveyed annually from 2013 to 2017. A companion study continues mail follow-up surveys of high school graduates at modal ages 19-30, 35, 40, 45, 50, and now 55. The study’s cohort-sequential longitudinal design permits the measurement and differentiation of three types of change: age (developmental), period (historical), and cohort. The study allows examination the importance of many hypothesis on psychological, behavioral, and social determinants of drug use (including attitudes and beliefs, counter-advertising, role-modeling, and access), as well as a range of potential consequences (including physical and psychological health, status attainment, role performance, and drug abuse and dependence).