We evaluated the prevalence of white coat (WC) effect in pediatric age patients and that of white coat hypertension (WCH) in hypertensive pediatric patients. Two hundred and six patients (136 normotensive and 70 hypertensive patients, 107 boys and 99 girls, aged 6-25 years, mean 13.4, SD 4.7) were studied. Hypertension was diagnosed when systolic and/or diastolic blood pressure (BP) measurements with auscultatory technique were >or= the 95th percentile for sex and age. WC effect was defined as office BP minus daytime mean ambulatory BP (ABP). WCH was diagnosed in the hypertensive patients when daytime ABP values were or= 10 mmHg was observed more frequently in hypertensive patients (50%) than in normotensive patients (25%). Among 70 hypertensive patients, 33 (47%) had WCH. There was no significant difference in the prevalence of WCH in relation to age, gender, or the presence or absence of causes of hypertension. In conclusion, WC effect is frequently seen in pediatric patients, and is more common in subjects with higher office BP.