The study found that the participants in the pilot program Anger Management for Female Juvenile Offenders (AMFJO) did not have significantly different treatment outcomes from the female juvenile offenders who received treatment as usual (TAU). This was expected due to the small sample size involved (12 girls randomly assigned to either AMFJO or TAU and only 5 of the girls available for the followup measures). For the purposes of this phase of the study, however, researchers were less interested in finding statistically significant differences between groups than in obtaining estimates of treatment effect sizes. Nearly all obtained effect sizes were in the medium-to-large range, suggesting promise for a larger scale evaluation. In addition, at pretreatment assessment, the treatment and control groups scored at slightly different levels on anger and aggression. This limitation should be corrected with an increase in the number of participants in a larger scale evaluation with a stratified random assignment procedure that accounts for participants' initial anger and aggression scores. Recommendations are offered regarding lessons learned for anger management interventions tailored to violent and aggressive female juvenile offenders. They pertain to nonphysical aggression in relationships, appropriate behaviors for strengthening and repairing damaged relationships, interventions that are developmentally appropriate, cultural awareness, teaching behavioral strategies, application of treatment lessons to real-life situations, and the co-occurrence of mental disorders and substance abuse with violent and aggressive behaviors. The AMFJO was piloted in a residential, female, postadjudication juvenile justice facility that housed approximately 50 girls. Each participant was administered instruments before and following treatment in order to assess anger, aggression, and mental health symptoms. 1 table, 7 figures, and 61 references