Evaluation of mean blood pressure values, ambulatory arterial stiffness index (AASI), pulse pressure (PP), blood pressure variability (BPV), and circadian blood pressure rhythm using ambulatory blood pressure monitoring (ABPM) in children with IgA nephropathy and Henoch-Schönlein nephropathy (IgAN/HSN). In 48 children (29 with IgAN, 19 with HSN) aged 14.04±3.76 years, we evaluated retrospectively 24-hour systolic and diastolic BP (24hSBP, 24hDBP), AASI, PP, systolic and diastolic BPV, and nocturnal BP dip by ABPM, body mass index (BMI) Z-score, medications, and biochemical parameters. The control group (CG) consisted of 20 healthy children aged 13.36±4.12 years. AASI was 0.369±0.100 in IgAN, 0.346±0.148 in HSN, and 0.300±0.067 in the CG; AASI was significantly (p=0.009) higher in IgAN vs. CG. PP was higher (P=0.04) in IgAN vs. HSN. Based on ABPM data, poorly-controlled hypertension was found in 14 of 22 patients (63.6%) with previously diagnosed hypertension. No differences in BPV or nocturnal BP dip were found between the groups. In all children with IgAN/HSN, 24hDBP correlated significantly with proteinuria, cholesterol, triglycerides, and prednisone dose; BMI Z-score correlated with SBPV, DBPV, and PP. 1. Children with IgAN have higher arterial stiffness compared to healthy peers. 2. In children with IgAN/HSN, proteinuria and hyperlipidemia are risk factors for elevated diastolic blood pressure, while obesity is a risk factor for increased blood pressure variability and pulse pressure. 3. Pediatric patients with IgAN/HSN require regular ABPM evaluation to allow for early detection of poor pharmacological control of hypertension. .