ABSTRACT: Background There are limited outcome studies of hypertension among young adults, especially using the new blood pressure ( BP ) categories from the American College of Cardiology and the American Heart Association. We examined associations between the new BP categories and the risk of incident cardiovascular disease ( CVD ) in low-risk and young adults. Methods and Results A cohort study was performed in 244 837 Korean adults (mean age, 39.0 years; SD , 8.9 years) who underwent a comprehensive health examination at Kangbuk Samsung Hospital from January 1, 2011, to December 31, 2016; they were followed up for incident CVD via linkage to the Health Insurance and Review Agency database until the end of 2016, with a median follow-up of 4.3 years. BP was categorized according to the new American College of Cardiology/American Heart Association (ACC/AHA) hypertension guidelines. During 924 420.7 person-years, 1435 participants developed new-onset CVD (incidence rate of 16.0 per 104 person-years). The multivariable-adjusted hazard ratios (95% CI s ) for CVD comparing elevated BP , stage 1 hypertension, stage 2 hypertension, treated and strictly controlled (systolic BP /diastolic BP <130/80 mm Hg with antihypertensive use), treated and controlled (systolic BP 130-139 and diastolic BP 80 to 89 mm Hg with antihypertensive use), treated uncontrolled, and untreated hypertension to normal BP were 1.37 (1.11-1.68), 1.45 (1.26-1.68), 2.12 (1.74-2.58), 1.41 (1.12-1.78), 1.97 (1.52-2.56), 2.29 (1.56-3.37) and 1.93 (1.53-2.45), respectively. Conclusions In this large cohort of low-risk and young adults, all categories of higher BP were independently associated with an increased risk of CVD compared with normal BP , underscoring the importance of BP management even in these low-risk populations.