The offspring of hypertensive parents in general show higher casual blood pressure levels during adolescence than the offspring of normotensive parents. Comparative ambulatory blood pressure measurements might reveal the stability and pattern of this difference during circadian blood pressure variation. We studied the 24-h ambulatory blood pressure (Space-Labs 90202 monitor, Redmond, Washington, USA) in youngsters with two hypertensive parents (high; n = 62), with one hypertensive parent (mixed; n = 51) and with no hypertensive parent (low; n = 42). The pattern for both systolic and diastolic blood pressure in the three groups ran parallel, with the high group continuously at a higher level. A clear difference in systolic blood pressure was observed during the day period (high minus low: 5.4 mmHg; 95% confidence range 2.5-8.3). Our data show that offspring of hypertensive parents differ in ambulatory blood pressure levels, but not in the circadian pattern, from the offspring of normotensive parents.