Girls face unique developmental challenges in childhood and adolescence. Compared to boys, girls tend to report more mental health problems, and they are susceptible to reproductive health risks, such as unwanted pregnancy and sexually transmitted disease. While a number of evidence-based programs have been found to be effective at reducing risk factors for children and adolescents, many programs have differential impacts for girls and boys. Understanding "what works" for girls is critical to improving outcomes youth. This brief and its companion brief, focused on boys, examine programs and strategies that work, as well as those that don't for each gender. This research brief synthesizes findings from 106 random assignment intent-to-treat evaluations of social interventions that targeted female children, adolescents, and young adults, or co-ed interventions that provide separate data about impacts for the female subgroup. Interventions were excluded from the review if they did not include at least 100 girls in the evaluation sample. Overall, 51 of the 106 programs had a positive impact for girls on at least one of the outcomes reviewed, 27 had mixed findings, and 28 did not have a positive impact on any of the outcomes studied. While several themes emerged within each outcome area, there was no approach that worked across all outcome areas. (Contains 48 footnotes.) [Additional funding for this paper was provided by the Alexander and Margaret Stewart Trust Foundation. For related report, "What Works for Male Children and Adolescents: Lessons from Experimental Evaluations of Programs and Interventions. Fact Sheet. Publication #2012-22," see ED535391.]