The frequency of resistant hypertension-defined as blood pressure (BP) ≥140/90 mm Hg with proven use of three antihypertensive medications, or as the use of four antihypertensive drug classes regardless of BP-is unknown in low-middle-income countries. Using data from the Brazilian Longitudinal Study of Adult Health, a cohort of 15,105 civil servants aged 35 to 74 years, the authors identified 4116 patients taking treatment for hypertension, 11% of who had resistant hypertension. These participants were more likely to be older, black, less educated, poorer, and obese. The adjusted prevalence ratios (95% confidence intervals) were diabetes, 1.44 (1.20-1.72); glomerular filtration rate (<60 mL/min/1.72 m(2) ), 1.95 (1.60-2.38); albumin-to-creatinine ratio (>300 mg/g), 2.43 (1.70-3.50); carotid-femoral pulse-wave velocity, 1.07 m/s (1.03-1.11 m/s); common carotid intima-media thickness, 2.57 mm (1.64-4.00 mm); left ventricular hypertrophy, 2.08 (1.21-3.57); and atrial fibrillation, 3.55 (2.02-6.25). Thus, the prevalence of resistant hypertension in Brazil is high and associated with subclinical markers of end-organ cardiovascular damage.