This document consists of a joint lecture/discussion co-delivered as the 1987 University Senior Research Scientist Lecture at the University of Michigan's Institute for Social Research. The opening remarks by Jerald G. Bachman describe how the program of research into drug use among youth and young adults evolved at the Institute for Social Research, and how the program developed its annual surveys of lifestyles and values of youth. Thereafter, Lloyd D. Johnston describes current research designs and procedures for the Monitoring the Future project, an annual survey of a representative sample of high school seniors, together with follow-up surveys of a subset of these students up to age 22 noting that the survey covers a wide range of topics and has taken place every year since 1975. He then presents a selection of findings relating to changes in the use of four specific drugs: marijuana, cocaine, cigarettes, and alcohol. Bachman follows with a discussion of patterns of change and stability in post-high school drug use. In particular, he discusses how changes in drug use relate to the new roles and responsibilities of young people after they leave high school. The final part of his talk focuses on how changes in marijuana use are linked to changing perceptions among young people of the risk involved in using it. The presentation includes 30 visual displays, some showing statistical data and trend analysis graphs. (TE)