Abstract The prevention of HIV in the United States is in a transformational era. In just a decade since the first finding of efficacy for daily oral PrEP, there is a proliferation of new PrEP agents, including long-acting injectable PrEP, and regimens, including “event-driven” (also called 2-1-1) PrEP. There has also been new knowledge about the impact of antiretrovirals (ARVs) for treatment of HIV, and an emergent understanding that people living with HIV who take ARVs and maintain a suppressed viral load are incapable of transmitting HIV to their sexual partners. In this context, the idea of “protected” sex – which historically meant sex protected by condoms – has become much more complex. To understand men’s preferences for prevention products and strategies and what choices are being made by men with varying risk profiles, we will enroll a prospective cohort of 1275 of men who have sex with men (MSM) in Atlanta, Detroit and San Diego and follow the cohort for two years. Each participant will have 8 quarterly quantitative assessments, including discreet choice experiments; a subset of MSM will be engaged in a qualitative assessments (focus group discussions and individual in-depth interviews) to help with message development and refinement. HIV and STI testing will be provided in alternating 6-month windows. Rapid reporting of results will produce actionable reports following each assessment wave. This project will serve as a dynamic source of data about the evolving patterns of use and preference for PrEP among MSM.