Most theorizing about desistance from antisocial behavior in late adolescence has emphasized the importance of individuals' transition into adult roles. In contrast, little research has examined how psychological development in late adolescence and early adulthood contributes desistance. The present study examined trajectories of antisocial behavior among serious juvenile offenders from 14 through 22 years of age and tested how impulse control, suppression of aggression, future orientation, consideration of others, personal responsibility, and resistance to peer influence distinguished between youths who persisted in antisocial behavior and youths who desisted. Different patterns of development in psychosocial maturity from adolescence to early adulthood, especially with respect to impulse control and suppression of aggression, distinguished among individuals who followed different trajectories of antisocial behavior. Compared with individuals who desisted from antisocial behavior, youths who persisted in antisocial behavior exhibited deficits in elements of psychosocial maturity, particularly in impulse control, suppression of aggression, and future orientation. (Contains 1 footnote, 6 tables, and 6 figures.)