This analysis examines the impact of the UNAIDS Investment Framework for HIV on adolescents to determine: a) impact of investing in prevention for adolescents 10-19 on new HIV infections, the number of adolescents living with HIV, and adolescent AIDS deaths; and b) cost of programs by type. We modeled four scenarios: (1) the Base scenario assumes constant coverage for prevention and treatment, (2) the Investment Framework scenario assumes scale-up of services to reach universal coverage targets by 2015, (3) the Investment Framework Delayed scenario assumes that coverage targets are not achieved until 2020, and (4) the Pessimistic scenario illustrates the disadvantages of poor implementation. Scaling up investments and services according to the Investment Framework could avert 2 million new adolescent HIV infections by 2020. A five-year delay would reduce impact by one-third. Poor implementation would result in little decline in the annual number of new infections. Achieving the Investment Framework will require a 45% expansion in annual expenditure to nearly $5.5 billion by 2014. After 2014 resource needs will decline somewhat due to reductions in new infections. One-third of these resources are for Basic Programs, one-fourth for Critical Enablers, and 40 percent for Development Synergies.