ABSTRACT: Importance:In December 2013, the panel members appointed to the Eighth Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC8) published a recommendation that non-Black adults initiate antihypertensive medication with a thiazide-type diuretic, calcium channel blocker, angiotensin-converting enzyme inhibitor (ACEI), or angiotensin receptor blocker (ARB), whereas Black adults initiate treatment with a thiazide-type diuretic or calcium channel blocker. ?-Blockers were not recommended as first-line therapy. Objective:To assess changes in antihypertensive medication classes initiated by race/ethnicity from before to after publication of the JNC8 panel member report. Design, Setting, and Participants:This serial cross-sectional analysis assessed a 5% sample of Medicare beneficiaries aged 66 years or older who initiated antihypertensive medication between 2011 and 2018, were Black (n?=?3303 [8.0%]), White (n?=?34?943 [84.5%]), or of other (n?=?3094 [7.5%]) race/ethnicity, and did not have compelling indications for specific antihypertensive medication classes. Exposures:Calendar year and period after vs before publication of the JNC8 panel member report. Main Outcomes and Measures:The proportion of beneficiaries initiating ACEIs or ARBs and, separately, ?-blockers vs other antihypertensive medication classes. Results:In total, 41?340 Medicare beneficiaries (65% women; mean [SD] age, 75.7 [7.6] years) of Black, White, or other races/ethnicities initiated antihypertensive medication and met the inclusion criteria for the present study. In 2011, 25.2% of Black beneficiaries initiating antihypertensive monotherapy did so with an ACEI or ARB compared with 23.7% in 2018 (P?=?.47 for trend). Among beneficiaries initiating monotherapy, the proportion filling a ?-blocker was 20.1% in 2011 and 15.4% in 2018 for White beneficiaries (P??.10 for interaction). Conclusions and Relevance:A substantial proportion of older US adults who initiate antihypertensive medication do so with non-guideline-recommended classes of medication.