ObjectiveDue to increased use of pre-exposure prohylaxis (PrEP) and its potential to affect HIV screening of blood donors, we undertook antiretroviral residual testing among HIV-negative male donors in England.MethodsResidual plasma samples were obtainnd from 46 male donors confirmed positive for syphilis and 96 donors who were repeat reactive for HIV antibodies in screening but confirmed as HIV-negative by reference testing. These were tested for concentrations of tenofovir and emtricitabine by high-performance liquid chromatograhpy coupled with mass spectrometry.ResultsWe found evidence of pre-exposure or post-exposure prophylaxis (PrEP/PEP) use in three male blood donors confirmed positive for syphilis (3 out of 46 screened, 6.5%). Two were estimated to have taken PrEP/PEP within a day of donating, and the third within 2 days. Two were new donors, whereas one had donated previously but acquired syphilis infection after his last donation.ConclusionsOur findings indicate that a small proportion of blood donors have not been disclosing PrEP/PEP use and therefore donating in non-compliance to donor eligibility criteria.