BACKGROUND: Tenofovir alafenamide (TAF) is a new formulation of tenofovir disoproxil fumarate (TDF) that was approved in 2015. While clinical trial evidence suggests that TAF has more favorable outcomes related to kidney injury and loss of bone mineral density, TAF also leads to higher lipid levels compared with TDF. OBJECTIVES: To (a) determine prescribing rates of TDF and TAF among new recipients from 2014 to 2018 in a large academic health system and (b) compare baseline patient characteristics of those newly prescribed TDF versus TAF before and after the approval of TAF in November 2015. METHODS: Electronic health record data were used to identify new recipients of TDF or TAF from 2014 to 2018 and describe their total monthly TDF and TAF prescriptions by indication. Patient characteristics were compared among new recipients of TDF before November 2015, new recipients of TDF after November 2015, and new recipients of TAF. RESULTS: Monthly TAF prescribing rates increased to match TDF prescribing rates by April 2018 (82 vs. 88 prescriptions per month). TAF recipients and new recipients of TDF before November 2015 had similar racial distributions; both of these groups were more likely to be Black compared with new recipients of TDF after November 2015 (55% and 53% vs. 37%; P < 0.0001). TAF recipients also tended to have more comorbidities, including chronic kidney disease (7% vs. 2% and 2%; P < 0.0001), hepatitis C virus (8% vs. 5% and 3%; P < 0.0001), diabetes (13% vs. 5% and 6%; P < 0.0001), hypertension (27% vs. 13% and 13%; P < 0.0001), coronary artery disease (5% vs. 3% and 2%; P < 0.0001), hyperlipidemia (21% vs. 6% and 7%; P < 0.0001), and congestive heart failure (3% vs. 1% and 1%; P < 0.0001), compared with both new recipients of TDF before and after November 2015. CONCLUSIONS: TAF prescribing rates grew substantially in the 2.5 years after FDA approval. TAF is being prescribed more often than TDF in patients with chronic kidney disease and in patients with cardiovascular disease, suggesting that prescribers may be prioritizing the kidney safety profile over the effect on lipids. DISCLOSURES: This work was supported by the Duke Clinical Research Institute Executive Director's Pathway for Supplemental Funding. The research team received additional support from the National Institute of Diabetes, Digestive, and Kidney Disease R01DK112258 and P01DK056492 (CW) and from the National Institute of Allergy and Infectious Diseases 5T32AI100851 (MHM). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Hung reports past employment by Blue Cross Blue Shield Association and CVS Health and a grant from Pharmaceutical Research and Manufacturers of America (PhRMA), unrelated to this work. The other authors have nothing to disclose. This work was accepted as a poster presentation for the AMCP Nexus 2020 Virtual, October 19-23, 2020.