Despite recent overall reductions in substance use, the non-medical use of prescription drugs is rising among adolescents and young adults. In 2001, young people reported past-year non-medical prescription drug use that exceeded the combined use of heroin, cocaine, crack, and hallucinogens. Among those aged 12-17, non-medical prescription drug use increased by 11.3 percent in 2001 from the previous year. In addition, first-time use of non-medical prescription drugs among individuals age 12-25 has been increasing, especially new use of prescription narcotics. To date, few studies have explicitly examined adolescents' and young adults' non-medical use and abuse of prescription drugs. Even less is known about the risk and protective factors for such use, despite emerging evidence that perceptions of risk and availability vary markedly by substance. The proposed study will fill these knowledge gaps by providing information that is useful to clinicians, treatment providers and decision-makers in identifying and preventing problematic use of abusable prescription drugs among adolescents and young adults. Using the "Web of Influence" model as a focusing framework, this study will address the following three specific aims: 1) document the prevalence and patterns of non-medical prescription drug use, abuse, and dependency, alone and in conjunction with other licit and illicit substances; 2) identify the risk and protective factors associated with non-medical prescription drug use; and 3) identify the risk and protective factors associated with the consequences of non-medical prescription drug use, namely abuse and dependency. Data to address these aims come from the 1999 - 2003 National Household Survey on Drug Abuse, the premier data source for estimating the prevalence of and risk and protective factors associated with substance use, including non-medical use, abuse, and dependency of prescription drugs. By the completion of this project, we will produce the first national-level estimates of the prevalence of prescription drug non-medical use, abuse, and dependency in adolescents and young adults, identify the associated and pertinent risk and protective factors, and provide an analytic foundation to develop predictive models for prescription drug non-medical use, abuse and dependency. Findings from this study will provide the basis for pursuing more extensive theoretical and empirical research into the unique problems of prescription drugs, and provide much-needed information for the development and implementation of successful prevention and education strategies aimed at ameliorating prescription drug abuse.