*Objective:* The aim of this study was to determine the gender differential in the relationship of body mass index (BMI) and abdominal obesity with blood pressure (BP) and prevalence of hypertension (HTN) and prehypertension (Pre-HTN) among the adult population of Iran.

*Design:* A nationwide cross-sectional survey was conducted from December 2004 to February 2005. The selection was conducted by stratified probability cluster sampling through household family members in Iran.

*Subjects and Measurements:* Weight, height, waist circumference (WC), and systolic and diastolic BP of 45,082 men and 44,322 women aged 15-65 (mean 39.2) were measured. 

*Results:* The prevalence of HTN was 25.2% in men and 24.8% in women; and 50.1% of men and 39.1% of women were pre-hypertensive. WC and BMI were strongly associated with BP in both genders. Multivariate analysis revealed that both WC and BMI had the stronger association with HTN and Pre-HTN in men than women. Compared to men and women with normal weight, the multivariate-adjusted odds ratio (OR) (95% confidence interval) of HTN was 5.75 (5.13, 6.44) for men and 4.29 (3.95, 4.66) for women with BMI ≥ 30. The multivariate OR of prevalence HTN in men with abdominal obesity compared with men without was 3.76 (3.41, 4.22) and in women, 2.92 (2.73, 3.13).

*Conclusion:* These data indicate that both BMI and WC had the stronger association with HTN and Pre-HTN in men than women. 

