Background: Prehypertension has been known to be closely associated with increased inflammatory markers and lipoprotein cholesterols, suggesting that it could promote an atherosclerotic process. The present study was purposed to compare carotid intima-media thickness (IMT) and its��� progression of during 2 years among subjects with different levels of blood pressure in a large population-based cohort. We further examined whether a short-term incidence and early treatment of hypertension with anti-hypertensive drugs could affect IMT progression. Methods: Subjects consisted of 2,255 general adults were derived from an ongoing population-based cohort study in Korea. Repeated measures of blood pressure and IMT on common carotid arteries (CCA-IMT) were performed at intervals of 2 years. IMT was measured by B-mode ultrasonogram on both sides. After excluding subjects who were treating with drugs, individuals were classified into three subgroups of blood pressure; normotensives (<120/80 mmHg), prehypertensives (120/80-139/89), and newly diagnosed hypertensives (���140/90). Results: At baseline examination mean and maximal CCA-IMTs were elevated in prehypertensives and newly diagnosed hypertensives, compared to normotensives. There was a dose-response relationship between CCA-IMT change during 2 years and increasing level of blood pressure, even after adjusting for covariates and baseline IMT. The 2-year incidence of hypertension in those with normotensives or prehypertensives was independently associated with an increased risk of faster progression of mean CCA-IMT. In addition, CCA-IMTs in subjects who were treated with anti-hypertensive drugs during 2 years were significantly less progressed or decreased compared with non-treated persons. Conclusions: The present study showed that prehypertensives as well as hypertensives could be exposed to fast progression of atherosclerosis, and short-term increase of blood pressure could also be a risk factor for atherosclerosis. Early treatment for newly diagnosed hypertensives was confirmed to have a protective effect for carotid atherosclerosis.