Since the 2015 WHO recommendation to offer pre-exposure prophylaxis (PrEP) to all at substantial risk for HIV infection as part of a comprehensive HIV prevention package, there have been significant efforts to expand PrEP access. By 2018, an estimated 465,000 individuals globally had initiated PrEP, a figure that while impressive falls short of the UNAIDS Prevention 2020 target of 3 million eligible people on PrEP by 2020. Achievement of the target will require an intensification of efforts to ensure more effective delivery of PrEP. Similar to the HIV treatment cascade which has been powerful in illustrating the steps needed to achieve viral suppression, several authors have proposed a ‘PrEP cascade’ which summarises the steps to successful PrEP initiation and in some, continuation. In this presentation we review how these cascades are helpful when populated with programme data for summarising progress as well as identifying points of attrition along the continuum. Using these cascades individual and structural barriers to achieving a particular step can be identified and programmes adapted or strengthened in response. PrEP cascade data can also be used to model the potential impact of PrEP programmes on the HIV epidemic. PrEP cascades also have several unique challenges not observed in treatment cascades. These include the problem of estimating the potential population eligible for PrEP (i.e. denominator), the absence of standard definitions which makes operationalisation within programmes and comparisons across programmes difficult, and the dynamic nature of risk which makes measurement of PrEP continuation a challenge.