Elevation of the urinary albumin excretion rate (AER) may be an important marker of vascular disease in nondiabetic as well as diabetic patients. Although hypertension is associated with an elevated AER, little is known regarding the relationship between AER and blood pressure in normal subjects. We studied 13 healthy, normotensive, nondiabetic subjects over 48 h. Urine was collected every 2 h and blood pressure was measured half hourly during the day using an ambulatory sphygmomanometric device. Overnight, blood pressure was measured hourly and a single overnight urine collection was obtained. Daytime blood pressures were higher than those overnight for systolic (122 +/- 9 v 105 +/- 8, P less than .01), diastolic (122 +/- 9 v 105 +/- 8, P less than .01) and mean arterial pressures (92 +/- 7 v 78 +/- 6 mm Hg, P less than .01). Similarly, AER fell overnight [day 5.9 (3.8 to 9.5) v night 3.6 (2.3 to 5.2) micrograms/min, median (interquartile range), P less than .01]. In the majority of subjects there was a significant positive correlation between AER and systolic (N = 9), diastolic (N = 10), and mean (N = 10) arterial pressure. We conclude that systemic blood pressure may influence AER in normal subjects.