Recent research on substance abuse has increasingly focused on the identification of distinct developmental trajectories of substance use. Research has also illuminated the high rates of substance abuse by individuals emerging into adulthood from late adolescence, often referred to as the period of “emerging adulthood.” The current study merged these two lines of research to compare how patterns of smoking, binge drinking, and marijuana use from early adolescence (age 13 years) to emerging adulthood (age 23 years) compare with key psychosocial and behavioral outcomes during emerging adulthood. First, the authors previous findings on patterns of smoking, binge drinking, and marijuana use among 6,527 participants aged 13 to 23 years were synthesized. The participants were then assigned to the trajectory class for each substance for which they had the highest probability of membership and logistic and least squares regression analyses were performed to model each of nine psychosocial and behavioral outcomes. Results indicated that early substance users were at a higher risk for deleterious outcomes at age 23 compared with later starters and abstainers. This finding remained even if the early users decreased their use during adolescence. Additionally, those who began substance use later but steadily increased their use over time also had a high risk for deleterious outcomes at age 23 years. More research is needed on how early and late adolescents differ from one another so that more effective prevention and intervention strategies may be developed. Figures, tables, notes, references