© American Journal of Hypertension, Ltd 2019. All rights reserved. RESULTS Among CARDIA study and JHS participants, 41.1% and 56.9% had nocturnal hypertension, respectively, and 32.4% and 72.8% had non-dipping SBP, respectively. The multivariable-adjusted prevalence ratios (95% confidence interval) for nocturnal hypertension associated with good, fair, and poor vs. very good health behavior scores were 1.03 (0.82–1.29), 0.98 (0.79–1.22), and 0.96 (0.77–1.20), respectively in CARDIA study and 0.98 (0.87–1.10), 0.96 (0.86–1.09), and 0.86 (0.74–1.00), respectively in JHS. The health behavior score was not associated non-dipping SBP in CARDIA study or JHS after multivariable adjustment. CONCLUSIONS A health behavior score was not associated with nocturnal hypertension or non-dipping SBP.BACKGROUND Several health behaviors have been associated with hypertension based on clinic blood pressure (BP). Data on the association of health behaviors with nocturnal hypertension and non-dipping systolic BP (SBP) are limited. METHODS We analyzed data for participants with ambulatory BP monitoring at the Year 30 Coronary Artery Risk Development in Young Adults (CARDIA) study exam in 2015–2016 (n = 781) and the baseline Jackson Heart Study (JHS) exam in 2000–2004 (n = 1,046). Health behaviors (i.e., body mass index, physical activity, smoking, and alcohol intake) were categorized as good, fair, and poor and assigned scores of 2, 1, and 0, respectively. A composite health behavior score was calculated as their sum and categorized as very good (score range = 6–8), good (5), fair (4), and poor (0–3). Nocturnal hypertension was defined as mean asleep SBP ≥ 120 mm Hg or mean asleep diastolic BP ≥ 70 mm Hg and non-dipping SBP as < 10% awake-to-asleep decline in SBP.