To serve as a tentative reference group for clinical health, 107 adults measured their systolic (S) and diastolic (D) blood pressure (BP) with an ambulatory Del Mar Avionics monitor (Irvine, California). Data were collected over approximately 24 hours at 7.5-minute intervals during waking and at 15-minute intervals during sleep. An echocardiogram served to determine the left ventricular mass (LVM), septal wall thickness (SWT), posterior wall thickness (PWT), ejection fraction (EjFr), and left atrial size (LAS). Each data series was analyzed by single cosinor. A statistically significant circadian rhythm (P less than 0.05) was found in 96 subjects (89.7 percent) for SBP and in 86 subjects (80.4 percent) for DBP. A population-mean cosinor reveals a highly significant circadian rhythm (P less than 0.001) for both variables in men (n = 44) as well as in women (n = 63), with an acrophase around 14:15. The double circadian amplitude, a measure of the total predictable change within a day, averages 10 (women) and 11 (men) mm Hg for DBP and 14 (women) and 17 (men) mm Hg for SBP. The midline-estimating statistic of rhythm (MESOR) of SBP is found to be higher for men (125 mm Hg) than for women (120 mm Hg), P = 0.018, whereas no difference in MESOR is found for DBP (71 mm Hg). A statistically significant correlation with age is found for the MESOR of SBP in both men (r = 0.352; P = 0.018) and women (r = 0.336; P = 0.007). The MESOR of SBP is also found to correlate with LVM in men (r = 0.300; P = 0.046), but not in women (r = 0.181; P = 0.153), whereas the MESOR of DBP correlates with LVM in women (R = 0.316; P = 0.011) but not in men (r = 0.117; P = 0.543). A positive correlation is also found between the MESOR of SBP and SWT as well as with EjFr, which is more prominent in women; between the MESOR of DBP and LAS, which is more prominent in men; and a negative correlation is found for women but not men between the circadian amplitude of both SBP and DBP and EjFr. Blood pressure excess (in mm Hg x h; hyperbaric index, briefly HBI; Halberg et al., 1984) was computed by comparing each profile to the upper 95 percent time-varying prediction limit of healthy peers.(ABSTRACT TRUNCATED AT 400 WORDS)