Ambulatory blood pressure monitoring has become increasingly popular for diagnosing and treating hypertension. However, data from normotensive subjects are needed for interpretation of hypertensive readings. Ambulatory blood pressure was monitored in 126 normotensive subjects (age range, 20 to 84 years). Mean systolic and diastolic blood pressure and blood pressure loads (percentage of systolic readings greater than 140 mm Hg and diastolic readings greater than 90 mm Hg) were obtained and interpreted. Mean awake systolic and diastolic pressures ranged from 125 +/- 10 to 137 +/- 17 mm Hg and 70 +/- 8 to 71 +/- 9 mm Hg, respectively. The systolic and diastolic trends of subjects' blood pressures taken during office visits and the 24-hour measurements were similar. Ranges for systolic and diastolic blood pressure loads from youngest to oldest ages were 9% +/- 14% to 25% +/- 20% and 3% +/- 7% to 4% +/- 7%, respectively. A comparison of blood pressure means from our sample that were taken during office visits and blood pressure means from a 2122-patient community survey demonstrated that our sample was reflective of an unselected population.