Hypertension is a frequent complication in patients with chronic renal insufficiency (CRI) and is associated with target organ damage, including left ventricular hypertrophy (LVH). To better assess hypertension in pediatric patients with CRI, we performed 24-h ambulatory blood pressure monitoring (ABPM) and evaluated the relationship between ABPM parameters and LVH in 29 children, mean age 12.4+/-3.8 years. There was no significant difference in the frequency of hypertension comparing casual systolic blood pressure (SBP) (21%) with the mean 24-h (21%) or daytime mean SBP (21%). However, diastolic hypertension was detected more frequently using ABPM: 24% for 24-h diastolic blood pressure (DBP), 14% for daytime DBP, and 7% for casual DBP. Nighttime systolic hypertension as well as diastolic hypertension was detected in 12 (41%) children. Seventeen (59%) patients had attenuated dipping for SBP and 9 (31%) had abnormal DBP dipping. Lower SBP dipping was associated with lower glomerular filtration rate (r=0.44, P<0.05). LVH was found in 6 (21%) patients. LVM index was significantly correlated with 24-h SBP (r=0.43, P<0.05). Multiple regression analysis confirmed that higher 24-h SBP was the only independent predictor for increased LVM index (P=0.001). No significant relationship was found between LVM index and office blood pressure. These results confirm a high prevalence of blood pressure abnormalities using ABPM criteria in children with CRI and suggest that ABP may better predict end-organ damage in these patients than casual BP.