Module Description: With the recent increase in use of vaping devices among youth, nicotine use disorder remains prevalent in adolescents and young adults. While rates of use of illicit stimulants including cocaine, ecstasy/MDMA and methamphetamine have decreased in adolescents in recent years, misuse of prescription stimulants remains common in this age group. This module reviews recent trends in nicotine and stimulant use in adolescents in young adults. It also presents a summary of the neurobiology of nicotine, discusses the different health effects and risks of harm of nicotine and stimulants (including illicit stimulants, prescription stimulants and caffeine) and offers an overview of prevention, harm reduction and treatment strategies for youth.