In response to a gap in gender-sensitive programming for young aggressive girls (5-11) and their families, the SNAP Girls Connection (GC) was developed in 1996. This multi-systemic intervention is built on a developmental model of risk and protective factors within the girl and her relationships. We evaluated the SNAP(R) GC using a prospective quasi-experimental design, randomly assigning 80 girls to treatment (N = 45) and waiting-list groups (N = 35) over 2 years. Fifty-five parents completed measures at assessment periods 1, 2 and 3. Results showed significant positive changes on girls' problem behavior and parenting skills for the treatment versus the waiting-list groups, as well as maintenance of treatment gains. Implications of the findings on treatment effectiveness of this gender-sensitive intervention are discussed.