Background: The prevalence of hypertension in various regions of the world has been widely reported. However, limited data are available about the incidence of hypertension in Korea. The purpose of this study is to estimate the incidence of hypertension over the 5-year in non-hypertensive subjects. Methods: Study subjects were 1,806 Koreans in a rural area in Daegu city, Korea. They were enrolled in the 2003 Daegu City Hypertension-Diabetes Survey from August to November 2003 for a cohort study. Of these patients, 1,286 (71.2%) individuals attended the 5-year follow-up examination, and 730 non-hypertensive individuals (265 males; mean age = 56.6짹11.1 year-old) at baseline examination were finally analyzed in this study. Primary endpoint was incident cases of hypertension, defined as either a new physician diagnosis or self-reports of newly initiated antihypertensive treatment. Results: During the 5-year follow-up, 195 (26.7%) non-hypertensive individuals developed incident hypertension. There was no significant difference in the incidence rate of hypertension by gender (23.0% in men and 28.8% in women, p=0.089). The age-adjusted 5-year incidence rates were 22.9% (95% confidence interval (CI) = 19.9-29.0) in overall subjects, 22.2% (95%CI = 17.2-27.2) in men, and 24.3% (95%CI = 20.4-28.2) in women. The incidence rates of hypertension significantly increased with age (17.9% in the age of 30-45 years, 19.7% in 45-54 years, 27.5% in 55-64 years, and 37.7% in 70 or more years; p for trend <0.001). The incidence rate of systolic hypertension significantly increased with age (p for trend <0.001), whereas the incidence rate of diastolic hypertension significantly decreased with age (p for trend =0.01). The crude incidence rates of hypertension in normotensive subjects were 16.6% in overall subjects, 14.5% in men, and 17.4% in women. The age-adjusted 5-year incidence rates of hypertension in normotensive subjects were 14.7% (95% CI = 12.2-17.3) in overall subjects, 12.5% (95%CI = 8.5-16.5) in men, and 16.1% (95%CI = 12.8-19.5) in women. The crude incidence rates of hypertension in prehypertensive subjects were 32.7% in overall subjects, 26.5% in men, and 37.0% in women. The age-adjusted 5-year incidence rates were 30.1% (95% CI = 26.8-33.4) in overall subjects, 26.4% (95%CI = 21.1-31.6) in men, and 32.2% (95%CI = 27.9-36.4) in women. Conclusions: About a quarter of non-hypertensives developed hypertension over the 5-year period. The incidence of hypertension increases with age and prehypertensives are twice as likely to develop hypertension as the normotensives.