The Implicit Theory project was designed to capture how HIV prevention providers delivering services think behavior change in their clients happens, what we refer to as providers’ implicit theories. This is important for many reasons. To begin with, the providers work directly with clients and were often peers of these clients. They are directly interacting with their clients and may be able to even witness when change has occurred. The providers’ position as peer or former peer, as the practice of hiring from the community that one wants to serve is very popular among HIV prevention organizations, is also key. This position provides insight and familiarity about the context and complexities of clients’ lives that is unique to providers. But the most compelling reason to capture this is that this is what providers are actually doing. Regardless of what researchers are studying or what funders are funding, we found that the providers we interviewed are out in the field acting on what they believe helps change behavior. Providers’ implicit theories drive their services, and therefore, it’s important to understand these implicit theories.