In 2017, definitions for pediatric hypertension were updated. A threshold of 130/80 mm Hg was introduced for stage 1 hypertension in adolescents, and children with obesity were removed from the reference population, lowering the 95th percentile, compared to the 2004 Fourth Report. The impact of these changes on care for youth with elevated blood pressure has not been well described. The objective of this study was to compare the 2017 and 2004 criteria for hypertension, evaluating how they impact estimates of risks for elevated blood pressure to progress to hypertension. Data came from youth 10-17 years of age with >/=2 elevated blood pressure measurements (>/=90th percentile or >/=120/80 mm Hg) between 04/15/2014 and 04/14/2016 and three additional measurements over two subsequent years. Blood pressures were recorded in primary care practices within a large health system, as part of routine care. Rates of incident hypertension following persistent elevated blood pressure based on the 2017 guidelines vs the 2004 Fourth Report were compared. We found, among 2025 youth with persistent elevated blood pressure, 46% were female and mean age was 14.6 years. Over 2 years of follow-up, progression to hypertension occurred in 5.9% using the 2017 guidelines vs 1.1% using 2004 Fourth Report definitions. Using the 2017 criteria, progression was most common in older youth and those with obesity. In conclusion, for most youth, elevated blood pressure does not progress to hypertension within 2 years. However, progression from elevated blood pressure to hypertension was more than 5-fold greater when applying the 2017 guidelines compared to the older 2004 Fourth Report criteria.