Abstract: This study examined the relationship between blood lead level and hypertension prevalence in a population-based sample of hypertensive and normotensive patients in the Shariatie and Imam Khomeini hospitals in Tehran, Iran. Cross sectional samples of 160 patients (age: 40-70), who participated in a physical examination from these hospital`s survey conducted from 2002-2003. The range of blood lead levels was 2.6 to 16.5 μg dL-1. The mean blood lead levels of hypertensive patients (5.1±0.4 μg dL-1) were higher than normotensive patients (2.6±0.3 μg dL-1). There was a significant difference in the mean blood lead levels of hypertensive men (5.6±0.61 μg dL-1) and normotensive men (2.2±4.3 μg dL-1) in this study. The comparison of blood lead levels of hypertensive women(4.7±0.6 μg dL-1) and normotensive women (2.3±0.5 μg dL-1) did also show a significant difference (p<0.001). In this population we concluded at levels well below the exposure limit guidelines (40 μg dL-1), blood lead levels are positively associated with both systolic and diastolic blood pressure and risk of both systolic and diastolic hypertension among patients aged 40 to 70 years.