Occasional high blood pressure (BP) readings in children are common; however, their clinical significance has not been carefully evaluated. In this study, we examined the association between childhood BP and adulthood hypertension in a prospectively followed cohort. The original cohort was established in 1986 and consisted of 1117 healthy children (528 male and 589 female), recruited from schools in Indianapolis, Indiana (mean age 12.1; SD 5.7 years). During the course of follow-up, BP was measured semiannually with a mean of 8.4 visits per child (SD 7.2). For the active subjects that were still being followed (n=263), diagnosis of hypertension was made based on JNC-7 criteria. For subjects no longer active in the study (n=854), we examined their adult medical records for physician-diagnosed hypertension. The mean age of the subjects as of 2013 was 33.4 years (SD 3.9). Among the adult subjects, there were 119 cases of hypertension (31 identified through prospective follow-up, 88 through chart review). We examined the childhood BP records of the study subjects using age, sex, and height adjusted BP percentile values; readings exceeding the 95th percentile were considered to be in a hypertensive range. In children with no BP measures exceeding the 95th percentile, the adult hypertension rate was 8.6% (82/959); in children with one BP measure in the hypertensive range, adult hypertension rate increased to 18% (20/110); in children with two or more BP measures in the hypertensive range, the adult hypertension rate was 35% (17/48). Adjusting for the effects of age, sex, and body mass index, we found that having at least one BP reading in the hypertensive range in childhood significantly increased the adult hypertension risk (adjusted odd ratio=3.1, 95%CI: 2.0-4.8). In addition, it is noteworthy that 59% (70/119) of those with hypertension as adults were either overweight or obese as children. In conclusion, episodic high BP in childhood significantly predicts adult hypertension risk. Occasional high BP readings should not be dismissed and modifiable risk factors should be addressed.