ObjectiveTo leverage qualitative data to explore gay and bisexual men’s (GBM) perceptions about doxycycline post-exposure prophylaxis (Doxy-PEP). Doxy-PEP is a novel biomedical STI-prevention strategy that helps reduce the risk of acquiring bacterial STIs. Little is known about Doxy-PEP’s acceptability in the U.S., nor how best to engage those most vulnerable to STIs in taking up this nascent prevention strategy. MethodBetween July and September of 2023, 24 GBM from across the U.S. completed qualitative interviews about their perceptions regarding Doxy-PEP. Interviews were analyzed using a codebook approach to thematic analysis. ResultsParticipants were generally interested in using Doxy-PEP, but were concerned about the potential for antibiotic resistance, side-effects, medication interactions to occur, along with stigmatizing discourse around its use. Meanwhile, participants were motivated by the simplicity of Doxy-PEP and the protection it could confer on both an individual and community-level— as well as its potential to reduce STI-related anxiety. Finally, participants desired additional information on Doxy-PEP to address their concerns. ConclusionsThere is a need for clear guidelines and expanded public health messaging on Doxy-PEP in the U.S.