This proposed study is an initiative for HIV prevention and care that integrates intervention efforts at multiple strata: Community Health Workers (CHWs), Injecting Drug Users (IDUs), and their Family Members (FMs). The proposed study will demonstrate the process of development, implementation, and evaluation of an intervention for CHWs, IDUs, and their FMs. One aim is to increase the CHWs' capacities to effectively interact with IDUs and FMs for HIV and drug use prevention and treatment. Using a combination of participatory action research and a randomized controlled trial design, this study has the potential to maximize PEPFAR impact in Vietnam and other PEPFAR-funded countries by identifying a sustainable mix of interventions and their implementation in different settings. The findings may benefit not only Vietnam but also a global audience by investigating enhanced methods for controlling the HIV epidemic.