Thus far, research indicates that treatment programs for justice-involved boys may provide a basic design for girls' programs, but they require modification and adaptation to meet the distinctive needs of justice-involved girls. There is a current lack of prospective and longitudinal data necessary to determine what interventions work for girls. Such research is required in order to determine which girls may experience negative adult outcomes, which girls will reduce their delinquent behavior without significant treatment, and what services are most effective with justice-involved girls. Research on the similarity of delinquency risk factors for boys and girls has not produced agreement. Some researchers have found a different set of risk factors for each gender, while others have concluded that the same set of risk factors predicts involvement in the justice system for both genders; however, regardless of this disagreement, once youths enter the justice system boys and girls often present different assessment profiles for intervention and have different needs. Girls are more likely than boys to have mental health needs, histories of victimization, chaotic family backgrounds, and a tendency to engage in nonphysical forms of aggression. The emergence of gender-specific programs for girls appears promising, especially if they include components based on both normative development and female delinquency. In order to determine what interventions work for girls, rigorous evaluations must be conducted. This chapter offers recommendations for the design of such evaluations. 61 references