Circadian rhythms in blood pressure in school-age children of normotensive and hypertensive parents. The purpose of this study was to describe the characteristics of blood pressure rhythms in school-age children and to compare the circadian mesors and amplitudes between children of normotensive parents and children of hypertensive parents. The sample consisted of 40 healthy children between 8 and 10 years old; 20 children had a parental history of hypertension and 20 did not. Blood pressure was measured every 2 hours during the day and every 90 minutes during the night for one 24-hour cycle using a Dinamap monitor equipped with an automatic printer. Cosinor analyses revealed statistically significant circadian rhythms for systolic and diastolic blood pressures in 12 of the 40 subjects. The acrophases for systolic and diastolic pressures occurred between 1200-1800 hours. The mean systolic mesor was 108.50 while the mean diastolic mesor was 61.41. The mean amplitudes were 8.85 for systolic pressure and 7.44 for diastolic pressure. No statistically significant differences in circadian mesors and amplitudes between children of normotensive parents and children of hypertensive parents were found. 