The Seventh Report of the Joint National Committee (JNC-7) introduced a new term "prehypertension" and it broadened the range of prehypertension to 120-139/80-89 mmHg. It is estimated that 31% of the US population and 29% of the Korean population have prehypertension. This condition is very prevalent and it's associated with other cardiovascular risk factors, especially obesity and diabetes. These people are at high risk for developing hypertension and subsequent cardiovascular events. Therefore, prehypertension has become a major public health concern, but the treatment standards have not yet been established. The JNC-7 report has recommended healthy lifestyles for all the people with prehypertension and it especially advocated drug treatment for the group of people with diabetes or chronic renal disease. This article reviews the prevalence of prehypertension, the risk and rate of progression to hypertension, the associated cardiovascular disease, the adverse cardiovascular events and the current status of treatment.