This article reports a comparison on outcomes of 26-year-old males who were defined severalyears ago in the Dunedin longitudinal study as exhibiting childhood-onset versus adolescent-onsetantisocial behavior and who were indistinguishable on delinquent offending in adolescence.Previous studies of these groups in childhood and adolescence showed that childhood-onsetdelinquents had inadequate parenting, neurocognitive problems, undercontrolled temperament,severe hyperactivity, psychopathic personality traits, and violent behavior. Adolescent-onsetdelinquents were not distinguished by these features. Here followed to age 26 years, thechildhood-onset delinquents were the most elevated on psychopathic personality traits,mental-health problems, substance dependence, numbers of children, financial problems, workproblems, and drug-related and violent crime, including violence against women and children. Theadolescent-onset delinquents at 26 years were less extreme but elevated on impulsive personalitytraits, mental-health problems, substance dependence, financial problems, and property offenses.A third group of men who had been aggressive as children but not very delinquent as adolescentsemerged as low-level chronic offenders who were anxious, depressed, socially isolated, and hadfinancial and work problems. These findings support the theory of life-course-persistent andadolescence-limited antisocial behavior but also extend it. Findings recommend intervention withall aggressive children and with all delinquent adolescents, to prevent a variety of maladjustmentsin adult life.