The USAID Health Policy Initiative, Task Order 1,developed several HIV modeling tools that can be used for various HIV and AIDS policy development andimplementation exercises. The tools are user-friendly Excel- or Windows-based models that can be used to help in-country partners understand the magnitude of health challenges,explore policy and resource options, and set priorities. The HIV modeling tools are designed to answer many questions, including "what if" questions related to resources, healthcare providers and services, and service coverage. The "what if" refers to factors that can be changed or influenced bypublic policy. This brief presents a summary of each HIV costing tool included in this package.