Abstract To reach Ending the Epidemic (ETE) targets, we will need consistent national HIV pre-exposure prophylaxis (PrEP) data to describe patterns of use, and to understand which programs and policies are effective at facilitating PrEP uptake. Our team has used national PrEP prescription datasets that combine diverse sources in order to better understand how PrEP is being brough to scale. National prescription datasets are robust and capture a great deal of data. We propose to develop the PREMISE (PrEP Epidemiology, Modeling, and Surveillance) group that will use national PrEP data, along with legal and policy coding, to inform the US HIV epidemic response. Legal and program environments in which individuals initiate PrEP are highly heterogeneous, yet evidence regarding which policies lead to improved outcomes is lacking. Our past work demonstrated a substantial association between PrEP use and the presence of PrEP drug assistance programs. ETE programs have expended considerable resources in HIV prevention promotion programming. Natural experimental designs can provide evidence regarding PrEP uptake in light of such programs. Such analyses require developing nuanced datasets of policies and programs. Our team has extensive experience in both PrEP program and policy data collection, allowing for rigorous assessment. The study will conduct analyses regarding the scope and equity of PrEP scaleup over time, and will perform analyses to explore the impact of different locality-specific programs and policies on PrEP starts and PrEP equity. We will use modeling and cost-effectiveness analyses to contextualize findings and facilitate dissemination