ABSTRACT. Objective: Social role transitions have been linked to changes in substance use and misuse during young adulthood. This study examined how commonly observed pathways to adulthood, defi ned by education, employment, marriage, and parenthood, were associated with alcohol, tobacco, and marijuana misuse from ages 18 to 33. Method: Data came from a longitudinal panel of 412 men and 396 women recruited when they were in fi fth grade in Seattle public schools in 1985. Participants were followed through age 33 in 2008, with 92% retention. Results: Young adults who had little postsecondary education and remained unmarried through age 30 generally had the highest rates of substance misuse. Those who were involved in postsecondary education and postponed family formation had the lowest rates, particularly with respect to daily smoking and nicotine dependence. Parenting during the young adult years was associated with lower rates of substance misuse for both men and women. However, taking on parenting responsibilities early, during the late teen years and early 20s (observed mostly for women), was associated with higher rates of tobacco misuse. Differences in substance misuse by pathways to adulthood were fairly constant across the young adulthood years and were already observed at age 18, suggesting that substance misuse patterns are established early. Conclusions: Young adults may change their substance use only partially in response to new freedoms and responsibilities in young adulthood. Preventive efforts should include a focus on early initiation of substance use and educational experiences that move people into life trajectories and associated substance misuse patterns. (J. Stud. Alcohol Drugs, 72,