For many adolescents today, the most common form of substance use is nonmedical prescription drug use. Fittingly, many researchers, policy makers, and people who work with youth are concerned about the serious problems associated with nonmedical prescription drug use (NMPDU). In this article, authors Jason Ford and William Watkins provide an overview of the research on adolescent nonmedical prescription drug use. They define NMPDU, discuss prevalence, identify demographic characteristics of users, review risk factors for use, and other important themes.