The primary purpose of this paper was to review systematically some of the more salient findings from a decade of research on the epidemiology of alcohol and drug abuse among adolescents. Data from most of the on-going nationwide studies regarding lifetime, past year, and past month use of various drugs were examined. While there is evidence of a downturn for some of the indicators, it is still too early to know if this is a temporary shift in rates or the beginning of meaningful trends toward lower levels of drug use. The second purpose was to challenge the alcohol and drug fields to consider more seriously the problem of multiple drug use and abuse. This was accomplished by showing that the relative percentage of youth who have used "only marijuana" has gone down as the percentage of youth who have used marijuana, other illicit drugs, and cigarettes and alcohol as well, has increased. Regression and discriminant analyses of data from the 1980 Monitoring the Future study of high school seniors reveals that variables that previously have differentiated users from nonusers are also useful in differentiating types of multiple drug users. The most important conclusion from this paper is that persons characterized as "daily" users of marijuana are better typed as multiple drug users.