Despite the promise of prevention and early intervention programs, research has shown that these policies rarely produce the expected results and more often have the opposite effect. Instead of reducing the number of youth formally processed through the juvenile justice system, these prevention and early intervention policies subject more youths to formal justice system intervention. Criminologists refer to this phenomenon as "net widening," and it is an increasing trend. The implications of net-widening are serious, because the process results in the diversion of resources from youth most in need of intervention to youths who may require no intervention. For the past 40 years, criminal justice research has consistently shown that almost 70 percent of youth who are arrested once are never arrested again; thus, by doing nothing, the state can achieve a 70-percent success rate with first-time offenders. By reducing net-widening, research shows that systems can improve their effectiveness and better promote public safety. Although programs must be developed for youths who are experiencing personal crises, these programs should be voluntary and remain unaffiliated with the justice system. The preferred models for effective justice-system intervention are programs that target high-end youths who have three or more justice-system contacts. The number of prior contacts remains the only reliable means of predicting the likelihood of future justice system involvement. An example of net-widening through juvenile justice reforms in San Francisco is provided. 1 figure and 1 table