 This study will evaluate the safety and acceptability of intermittent and daily pre-exposure prophylaxis PrEP regimens with FTCTDF emtricitabinetenofovir disoproxil fumarate in HIV discordant couples, and it will directly compare adherence and intracellular drug levels in daily and intermittent PrEP recipients. It will also evaluate the relationship between drug adherence, sexual behavior and intracellular drug levels with an intermittent PrEP regimen. In addition it will evaluate the relationship between adherence to an intermittent PrEP regimen and timing of sexual activity in relation to PrEP dosing. The pilot will use objective medication event monitoring MEMS adherence measurement and evaluate the feasibility of newer adherence measurements such as hair sampling and plasma drug levels. This study will also evaluate the feasibility of using text messaging SMS to collect sexual activity data in an African setting. It will allow study teams and communities to prepare for potential subsequent larger trials of intermittent PrEP. The study is not sized to evaluate efficacy. If the intermittent PrEP regimen is safe, feasible in terms of adherence, and achieves intracellular drug levels similar to daily PrEP, the data could be used to design a larger phase 2 study with one or more intermittent PrEP regimens. The goal of such a larger trial would be to provide bridging data if daily PrEP regimens are found to be effective or to prepare for efficacy or non-inferiority trials of intermittent versus daily PrEP. 