In 2018, the American Heart Association published a Scientific Statement on resistant hypertension. We compared the prevalence of apparent treatment-resistant hypertension (aTRH) among US adults as defined in the 2018 and 2008 American Heart Association Scientific Statements using data from 4158 participants with hypertension, taking antihypertensive medication in the 2009 to 2014 National Health and Nutrition Examination Survey. Blood pressure (BP) was measured 3 times, and antihypertensive medication classes were identified through a pill bottle review. In both Scientific Statements, aTRH was defined as uncontrolled BP while taking ≥3 classes of antihypertensive medication or taking ≥4 classes of antihypertensive medication regardless of BP level. Uncontrolled BP was defined as systolic/diastolic BP ≥140/90 mm Hg (≥130/80 mm Hg for those with diabetes mellitus or chronic kidney disease) in the 2008 Scientific Statement and systolic/diastolic BP ≥130/80 mm Hg (systolic BP ≥130 mm Hg only for low-risk adults ≥65 years of age) in the 2018 Scientific Statement. The prevalence of aTRH was 17.7% and 19.7% according to the 2008 and 2018 Scientific Statement definitions, respectively (Δ=2.0%; 95% CI, 1.5%-2.7%). Overall, 10.3 million US adults had aTRH according to the 2018 Scientific Statement. The most common 3-drug combination taken included an angiotensin-converting enzyme inhibitor, β-blocker, and thiazide diuretic. Using the 2018 definition, 3.2% of US adults with aTRH were taking a thiazide-like diuretic (chlorthalidone or indapamide), and 9.0% were taking a mineralocorticoid receptor blocker (spironolactone or eplerenone). In conclusion, the prevalence of aTRH is only modestly higher using the definition in the 2018 versus 2008 resistant hypertension Scientific Statement.