The inspiration for this report was the rising interest in investing in the poorest girls in the poorest communities as a vital strategy for interrupting intergenerational poverty promoting positive health (maternal child HIV reduction) and achieving fertility goals. Investment in the most disadvantaged girls does not have to cost a lot to realize positive outcomes for girls and benefits for whole communities especially once effective programs have been established and expanded. This report is intended to assist programmatic officers technically involved donors and policy analysts in making program and policy decisions on investments in adolescent girls. It does so by providing an understanding of the appropriate expectations and frameworks through which to consider the costs of adolescent girls’ programs.