The theory of emerging adulthood has been proposed as a way of conceptualizing the developmental characteristics of young people between the ages of 18 and 25. Here, the theory is applied to explaining the high rates of substance use in this age group. Specifically, five developmentally distinctive features of emerging adulthood are proposed: the age of identity explorations, the age of instability, the age of self-focus, the age of feeling in-between, and the age of possibilities. Then, each of these features is applied to an explanation of drug use in emerging adulthood.