Background Despite early operation, persistent and late systolic hypertension are common among children and adolescents after surgical repair of aortic coarctation and can contribute to early cardiovascular morbidity. Methods Ambulatory blood pressure monitoring was performed for 78 patients (aged 3.6-22.8 years, 41 male) after successful surgical repair of aortic coarctation (median duration of follow-up 6.5 years, range 0.7-20.1 years). Hypertension was defined as mean systolic blood pressure exceeding the 95th percentile for sex and height. Results Twenty-three patients (29%) exhibited systolic hypertension during daytime, Hypertensive patients had been older at the time of operation than had normotensive patients (5.4 +/- 5.0 versus 2.4 +/- 3.1 years, P < 0.01). Prevalence of hypertension was 21% among patients who had undergone surgery during the first year of life and 38% among patients who had been operated upon later, Decline in blood pressure during night was similar for all patients (systolic 11 +/- 5% and diastolic 19 +/- 8%). Systolic hypertension during night-time was found in 24% of patients who were normotensive during day, Diastolic hypertension was rare. Follow-up measurements were performed for 41 patients after 2.3 +/- 1.3 years, and most normotensive patients remained normotensive during this time. Conclusions Ambulatory blood pressure monitoring allows one to estimate nocturnal hypertension in children and adolescents after surgical repair of aortic coarctation which is common also among normotensive patients during daytime. Blood Press Monit 5:163-167 (C) 2000 Lippincott Williams & Wilkins.