Those youth ages 15 and older who first begin antisocial behaviors serious enough to place them at risk for arrest are likely to desist from such behavior in the natural progress of maturation and as they assume the normative responsibilities of employment and family. Such youth generally have internalized moral standards, stable mental health, and well-developed social and intellectual skills. Prevention efforts for this group include helping them to learn resistance to negative peer pressure, training their parents to monitor their children more closely, helping to modify the stresses under which families may be struggling, making the youth accountable for their delinquent behavior, and channeling them into structured activities that emphasize positive values and behaviors. The second age group of youth identified are those who engage in serious antisocial behavior prior to age 15. These children tend to overwhelm their parents' ability to manage their children's behaviors effectively, and the youth were more likely to have free time in which they are unsupervised, tending to form or participate in deviant peer groups. They are arrested at an early age, and those who have committed three or more offenses are at much greater risk for committing violent crime. For these youth, prevention programs must begin at the earliest sign of persistent aggression and inability to conform to the behavioral standards set for them by parents, preschools, and elementary schools. This report describes strategies and prevention programs that have been effective with these youth. 33 references and 4 tables