Pre-exposure prophylaxis (PrEP) involves the use of antiretroviral agents, namely those commonly used in the treatment of HIV, to prevent HIV infection. HIV-negative persons engaging in behaviours that place them at high risk for HIV infection can substantially decrease this risk through the use of PrEP. In the Netherlands, both men who have sex with men and transgender persons with additional risk factors for HIV infection, such as having anal sex without the use of a condom with casual partners, are key groups that could benefit from PrEP. Previous research has shown that PrEP prevents HIV effectively, if taken as prescribed, and is safe to use. In this thesis, we discuss various aspects of implementing PrEP among men who have sex with men and transgender persons in the Netherlands. In particular, we aimed to shed light on whether the use of PrEP is associated with changes in sexual behaviour and the incidence of sexually transmitted infections, including hepatitis C virus. We use data from the Amsterdam PrEP demonstration project (AMPrEP), which started in 2015 with the intent of assessing PrEP uptake, and acceptability and usability of PrEP in HIV-negative men who have sex with men and transgender persons. One innovative part of AMPrEP’s design is that participants were offered a choice of regimen: daily use of PrEP (one tablet once daily) or event-driven use (consisting of two tablets before having sex, followed by one tablet 24 hours and one tablet 48 hours later). Additional specific aims of this thesis are to evaluate the attitudes of healthcare professionals towards PrEP implementation and to study the adoption of health technology in order to monitor adherence.