Brain natriuretic peptide (BNP) level has been used as a marker of left ventricular (LV) systolic dysfunction (LVSD), even though some patients with atherosclerosis have a high BNP level irrespective of LV function. In this study, we investigate whether augmentation index (AI), which is an index of wave reflection, is involved in increasing BNP level in hypertensive patients without LVSD. Sixty treated hypertensive patients were enrolled in this study. Radial AI (r-AI) was measured in all patients. The patients were classified into tertiles on the basis of r-AI to identify the characteristics of the patients with a high r-AI. BNP level was significantly higher in the patients classified into the highest tertile of r-AI. In echocardiography, e', which is index of left ventricular (LV) diastolic function, decreased and LV mass index (LVMI) increased gradually with r-AI, whereas there was no difference in LV ejection fraction (LVEF). r-AI significantly correlated with LVMI (r=0.35, p<0.01) and e' (r=-0.30, p<0.05). In univariate analysis, age, heart rate, r-AI, LVEF, e' and LVMI were significantly correlated with BNP level, whereas multivariate analysis demonstrated that only r-AI and LVEF correlated with BNP level. In conclusion, an increase in r-AI was significantly associated with an increase in BNP level in hypertensive patients without LVSD. LV hypertrophy and diastolic dysfunction associated with increase in r-AI may be involved in increase in BNP level.