Behavior and psychological problems assessed prospectively by teachers and parents and by youths' self-reports through late childhood and adolescence were examined as possible predictors of early adult depression. Data were from 765 participants in the Seattle Social Development Project, a multiethnic and gender-balanced urban sample. Analyses examined 7 waves of data from ages 10 to 21, and included measures from the Achenbach Child Behavior Checklist and assessments of past-year depressive episode based on the Diagnostic Interview Schedule. Self-reported conduct problems as early as age 10 (Mason et al., 2001) and throughout adolescence consistently predicted depression at age 21. Parent reports of conduct and other externalizing problems in adolescence also significantly predicted adult depression. None of the available teacher reports through age 14 were significant predictors. Results suggest that externalizing problems can be useful indicators of risk for adult depression. Prevention efforts that target externalizing problems in youth may hold promise for reducing later depression.