BACKGROUND: High waist circumference (WC) (women: >88 cm; men: >102 cm) increases cardiovascular risk. Less is known about moderate WC (women: 80-88 cm; men: 94-102 cm). Therefore, we examined the association between moderate WC and hypertension prevalence, independent of body mass index (BMI). METHODS: Among 24,247 eligible adults 45-84 years old, when recruited from January 2003 to October 2007 in the population-based REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort, we examined hypertension prevalence (systolic blood pressure (BP) ≥140 mm Hg, or diastolic BP ≥90 mm Hg, or self-reported antihypertensive medication use) by WC before and after stratification by BMI (normal: 18.5-24.9; overweight: 25-29.9; obese class I: 30-34.9). Logistic regression adjusted associations between WC, BMI, and hypertension prevalence for age, race, sex, region, income, education, cigarette smoking, glomerular filtration rate, alcohol use, and physical activity. RESULTS: Overall, hypertension prevalence was 44% among those with low WC (n = 8,068), 55% with moderate WC (n = 6,488), and 66% with high WC (n = 9,691). After full adjustment, moderate WC was independently associated with hypertension prevalence among persons with normal BMI, (adjusted odds ratio (aOR), 1.49; 95% confidence interval (CI), 1.31-1.70), overweight BMI (aOR, 1.80; 95% CI, 1.64-1.98), and obese class I BMI (aOR, 2.28; 95%CI, 1.96-2.65) (referent: low WC-normal BMI). The moderate WC-hypertension association was observed in blacks and whites and in men and women. CONCLUSION: Moderate WC is associated with hypertension prevalence independent of BMI and several hypertension risk factors in middle-aged and older adults.