In this prospective study of upper middle class youth, we document frequency of alcohol and drug use, as well as diagnoses of abuse and dependence, during early adulthood. Two cohorts were assessed as high school seniors and then annually across 4 college years (New England Study of Suburban Youth younger cohort [NESSY-Y]), and across ages 23–27 (NESSY older cohort [NESSY-O]; ns = 152 and 183 at final assessments, respectively). Across gender and annual assessments, results showed substantial elevations, relative to norms, for frequency of drunkenness and using marijuana, stimulants, and cocaine. Of more concern were psychiatric diagnoses of alcohol/drug dependence: among women and men, respectively, lifetime rates ranged between 19%–24% and 23%–40% among NESSY-Os at age 26; and 11%–16% and 19%–27% among NESSY-Ys at 22. Relative to norms, these rates among NESSY-O women and men were three and two times as high, respectively, and among NESSY-Y, close to one among women but twice as high among men. Findings also showed the protective power of parents’ containment (anticipated stringency of repercussions for substance use) at age 18; this was inversely associated with frequency of drunkenness and marijuana and stimulant use in adulthood. Results emphasize the need to take seriously the elevated rates of substance documented among adolescents in affluent American school communities.