Using data from the Columbia County Longitudinal Study, a 40-year longitudinal study following an entire county's population of third-grade students from age 8 to 48, we examine questions about the long-term consequences of aggressive and antisocial behavior in childhood, adolescence, and young adulthood. We found moderate levels of continuity of aggression from age 8 to 48 both for males and for females. Contrary to what some have proposed, we found that continuity of aggressiveness is owing to not only the high-aggressive participants staying high but also owing to the low-aggressive participants staying low. Compared with life-course-persistent low aggressives, we found that life-course-persistent high aggressives had consistently poorer outcomes across domains of life success, criminal behavior, and psychosocial functioning at age 48 (e.g., arrests, traffic violations, aggression toward spouse and divorces, depression, health, occupational and educational attainment). In contrast, adolescent-limited and child-limited aggressives did not differ from life-course-persistent low aggressives on the age 48 outcomes. Finally, the outcomes for late-onset (early adulthood) aggressives were also problematic in some domains though not as problematic as those for life-course-persistent aggressives. Aggr. Behav. 35:136–149, 2009. © 2009 Wiley-Liss, Inc.