The majority of HIV-1 infected patients in resource rich countries receive the tenofovir prodrug tenofovir disoproxil fumarate (TDF) as part of their combination antiretroviral therapy (cART). Long-term exposure to TDF can be associated with an accelerated estimated glomerular filtration rate (eGFR) decline and proximal renal tubular dysfunction (PTD, see definition below). The current practice in patients in which TDF related renal toxicity becomes apparent is to substitute abacavir (ABC) for TDF. However, ABC is contraindicated in patients with HLAB57*01 and has been associated with an increased risk of cardiovascular disease in large HIV cohort studies, but not in randomized clinical trials. Recently, a new tenofovir prodrug, tenofovir alafenamide (TAF) was developed by Gilead Sciences and is available in a coformulation with emtricitabine (FTC). Due to the targeted delivery of tenofovir inside the CD4 positive cell by this prodrug, only 25 mg TAF is needed for the same antiviral effect observed in patients taking 250 mg of TDF and this lower TAF dose leads to 90% lower serum levels of tenofovir. In recently completed phase III studies in which patients with a normal kidney function where included, this lower tenofovir exposure in patients on TAF was shown to prevent off-target renal and bone toxicity in comparison with patients taking TDF. However, whether an already established TDF related renal toxicity in a HIV patient can be reversed after a switch to TAF, remains to be shown.