Variations of systolic and diastolic blood pressure in patients with normotension at rest after successful surgical repair of coarctation of the aorta were examined using 24 hour ambulatory monitoring at mid-term follow-up. Ambulatory blood pressure monitoring, m-mode measurements of left ventricle and transmitral Doppler spectrals in 18 patients aged 7.6 +/- 4.5 years after 9 months to 6.1 years (2.5 +/- 1.9 years) following operation were compared with the findings in 18 matched controls. Patients had significantly higher mean systolic blood pressures (24 hours: 115 +/- 10 mmHg, awake: 119 +/- 11 mmHg and asleep: 106 +/- 8 mmHg) than controls (24 hours: 108 +/- 6 mmHg, awake: 112 +/- 7 mmHg and asleep: 101 +/- 7 mmHg) (p = 0.04, 0.03 and 0.03, respectively). Patients had also more systolic blood pressure readings above the 95th percentile for age (24 hours: 28 +/- 20%, awake: 39 +/- 27% and asleep: 12 +/- 14%) than controls (24 hours: 10 +/- 9%, awake: 14 +/- 13% and asleep: 1 +/- 4%) (p = 0.03, 0.002 and 0.007, respectively). No significant difference was found in diastolic blood pressure profiles. There were no significant differences in left ventricular m-mode measurements and diastolic function parameters. Left ventricular mass index was significantly increased in patients (81.7 +/- 28.7 g/m2) compared with controls (64.5 +/- 20.9 g/m2) (p = 0.03). Operation age and post-surgical period did not affect ambulatory blood pressure profiles at mid-term follow-up. Patients who are normotensive at rest after successful surgical repair of coarctation of the aorta show higher systolic blood pressure profiles than healthy children with ambulatory blood pressure monitoring at mid-term follow-up. Ambulatory blood pressure monitoring in patients operated on for coarctation of the aorta despite their good clinical status is useful to detect and monitor subtle abnormalities of blood pressure.