To determine the prevalence of hypertension (HTN) and its risk factors, we performed a population-based national cross-sectional blood pressure (BP) survey in Korea in 1990. Through cluster sampling, we selected for study individuals older than 30 years of age in 190 of 154,082 districts. Among 25,567 eligible individuals, 21,242 subjects had measurements of BP and body mass index (BMI) and underwent a standard interview. BP was recorded as the mean of two measurements on a standard mercury manometer. The prevalence of HTN varied widely by area of residence. Overall prevalence was 19.8% for HTN defined as BP greater-than-or-equal-to 140/90 mm Hg or subject on medication, and 12.4% for BP greater-than-or-equal-to 160/95 mm Hg or subject on medication. Correlates for HTN identified by logistic regression analysis included positive family history of HTN (odds ratio [OR] = 2.2,), age (10 years); OR = 1.9), alcohol intake (500 cc; OR = 1.4), urban location (versus rural; OR = 1.3), and BMI (1 BMI unit; OR = 1.2).