McCabe SE, et al. - This study was undertaken to determine if there was a link between sources of nonmedical use of prescription drugs (NMUPD), like anxiolytics, opioids, and stimulants, and sociodemographic features, NMUPD characteristics (eg, frequency), and other substance use. By self-administered questionnaires (2009–2016), nationally representative samples of US high school seniors (N=18,549) were surveyed. They used design-based latent class analysis and Rao-Scott χ2 tests to examine relationships among sociodemographic features, NMUPD characteristics, other substance use behaviors (eg, binge drinking, cigarette smoking, marijuana use), and NMUPD sources (friend/relative sources, friend/purchased sources, own leftover prescription, multiple sources, and other sources). According to findings, past-year NMUPD (n=1,917) was reported by approximately 11.0% of high school seniors. Non-medical consumers who were teenage boys were more likely to get prescription drugs from a friend/purchased sources, while teenage girls were more likely to use their own prescriptions. Patients and their families should receive training on how to manage and properly dispose of controlled medications to avoid community diversion. When prescribing controlled medications, prescribers should check prescription monitoring programs and screen adolescents for substance use/misuse.