['To identify novel biomarkers associated with pediatric primary hypertension.', 'We recruited 350 participants (4-16 years). Anthropometric parameters and aldosterone, plasma renin activity, cortisol, cortisone, Homeostasis Model Assessment Insulin Resistance (HOMA-IR), high-sensitivity C-reactive protein, adiponectin, IL-6, plasminogen activator inhibitor type 1 levels and matrix metalloproteinase-9 and matrix metalloproteinase-2 (MMP-9 and MMP-2) activities were measured. Genomic DNA was isolated. Patients with altered glucose metabolism, severe obesity [BMI-SD score (BMI-SDS)\u200a>\u200a2.5], renovascular disease, primary aldosteronism and apparent mineralocorticoid excess syndrome were excluded.', 'In selected participants (n\u200a=\u200a320), SBP was positively correlated with BMI-SDS (r\u200a=\u200a0.382, P\u200a<\u200a0.001), HOMA-IR (r\u200a=\u200a0.211, P\u200a<\u200a0.001), MMP-9 activity (r\u200a=\u200a0.215, P\u200a<\u200a0.001) and the cortisol/cortisone ratio (r\u200a=\u200a0.231, P\u200a<\u200a0.001). DBP showed similar correlations with these variables. No correlation was observed with aldosterone or plasma renin activity. Participants were categorized as hypertensive (n\u200a=\u200a59) or nonhypertensive (n\u200a=\u200a261). In the univariate analysis, hypertensive patients had higher BMI-SDS (P\u200a<\u200a0.001), HOMA-IR (P\u200a<\u200a0.001), high-sensitivity C-reactive protein (P\u200a<\u200a0.001), MMP-9 activity (P\u200a<\u200a0.001), plasminogen activator inhibitor type 1 (P\u200a<\u200a0.001) and cortisol/cortisone ratio (P\u200a<\u200a0.001) than nonhypertensive patients. Multiple regression analysis showed that the variables that remained associated with hypertension were higher BMI-SDS [odds ratio (OR)\u200a=\u200a3.74; 95% confidence interval (CI)\u200a=\u200a1.84-7.58], a higher cortisol/cortisone ratio (OR\u200a=\u200a3.92; 95% CI\u200a=\u200a1.98-7.71) and increased MMP-9 activity (OR\u200a=\u200a4.23; 95% CI\u200a=\u200a2.15-8.32).'] Are cortisol/cortisone ratio and matrix metalloproteinase-9 activity associated with pediatric primary hypertension?