Hulstein SH, Matser A, van der Loeff MFS, et al. - Among men who have sex with men in Amsterdam, the Netherlands, the present study was performed to evaluate the eligibility for, intention to use, and informal use of HIV preexposure prophylaxis (PrEP). Researchers included informal PrEP users (use without a prescription) in a cohort study (Informal PrEP [InPrEP]) at the Amsterdam Sexually Transmitted Infections (STI) Clinic between September 2017 and August 2018. PrEP use, PrEP eligibility and intention, chemsex, and STI positivity were compared between three groups: informal PrEP users enrolled in InPrEP, nonenrolled informal PrEP users, and non-PrEP users. Among non-PrEP users who were eligible for PrEP, intention and related traits were evaluated. There were 118 informal PrEP users who were enlisted in InPrEP that were compared with 224 nonenrolled informal PrEP users and 4,975 non-PrEP users. The data exhibited that the majority of informal PrEP users are eligible to use PrEP and have a clear need for sexual healthcare. Preexposure prophylaxis eligibility rates were 83.1%, 93.4%, and 63.0%, respectively. Among PrEP-eligible STI clinic visitors, the intention to use PrEP is low. Future studies should evaluate modes to increase PrEP intention among PrEP-eligible persons.