OBJECTIVE To examine whether plasma levels of brain natriuretic peptide identify hypertensive patients at risk for progressive cardiac hypertrophy. METHODS We examined the association between plasma brain natriuretic peptide levels and left ventricular structural changes in 54 hypertensive patients and 28 normotensive control subjects. Patients were divided into those with elevated (n = 14) or normal (n = 40) levels of brain natriuretic peptide, based on a cutoff level of 41 pg/mL (2 SD above the mean in the control subjects). Left ventricular function and geometry were assessed echocardiographically at baseline and follow-up. RESULTS At baseline, initial left ventricular chamber size, wall thickness, and systolic function did not differ between the hypertensive patients and normotensive subjects. After a mean (+/- SD) follow-up of 9 +/- 3 months, blood pressure was relatively unchanged in the hypertensive patients with normal brain natriuretic peptide levels, whereas there were significant increases in systolic blood pressure and pulse pressure (both P <0.05 versus baseline) in patients with elevated brain natriuretic peptide levels. Moreover, left ventricular midwall systolic function had decreased significantly at follow-up in those with elevated levels (P <0.05 versus baseline). At follow-up, the hypertensive patients with elevated brain natriuretic peptide levels had a significantly greater left ventricular mass index and relative wall thickness than those with normal levels. Multiple regression analyses determined that only initial plasma brain natriuretic peptide was significantly (P <0.01) associated with subsequent left ventricular hypertrophy. CONCLUSIONS Plasma brain natriuretic peptide levels may identify hypertensive patients who are likely to have progressive cardiac hypertrophy.