Table 1 Eligibility requirements

1. Born to male gender, age 18 years or older 2. Previously attended the enrolling clinic on at least one occasion 3. Completed a screen for HIV and STIs 4. HIV-negative by a routinely used assay within 4 weeks prior to or on the day of randomisation 5. Reported unprotected anal intercourse (UAI) on more than one occasion within the 90 days prior to randomisation 6. Likely, in the opinion of the volunteer, to have UAI in the next 90 days 7. Willing and able to comply with the visit schedule throughout the follow-up period 8. Willing and able to provide written informed consent

1. An acute viral illness that could be due to HIV seroconversion 2. Any contraindications to Truvada according to the current package insert 3. Treatment for hepatitis B infection indicated or ongoing 4. Unlikely, in the opinion of the clinician, to comply with the randomised allocation