Leptin is an adipose tissue-derived hormone shown to be related to metabolic, inflammatory, and hemostatic factors involved in hypertension development. Animal studies suggest that higher leptin levels may activate the sympathetic nervous system and cause elevations in blood pressure (BP). However, few studies have examined the association between leptin and hypertension in humans. Also it is not clear whether this association is present among women as well as men. Therefore, we examined the association between plasma leptin levels and hypertension in a representative sample of US adults. We examined the third National Health and Nutrition Examination Survey participants >20 years of age (n=5599; 54.7% women). Plasma leptin levels were categorized into quartiles (women: <7.68, 7.68 to 13.18, 13.19 to 21.70, >21.70 fg/L; men: <2.64, 2.64 to 4.36, 4.37 to 7.12, >7.12 fg/L). Hypertension was defined as BP-reducing medication use or having systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg. We found that higher plasma leptin levels were positively associated with hypertension after adjusting for age, sex, race/ethnicity, education, smoking, alcohol intake, body mass index, diabetes mellitus, serum cholesterol, and C-reactive protein. Compared with quartile 1 of leptin (referent), the odds ratio (95% CI) of hypertension associated with quartile 4 was 1.89 (1.24 to 2.09; P for trend=0.0036). Subgroup analyses examining the relation between leptin and hypertension by sex and body mass index categories also showed a consistent positive association. In conclusion, higher plasma leptin levels are associated with hypertension both among women as well as men in a representative sample of US adults.