Increased B-type natriuretic peptide (BNP) expression precedes the development of hypertension in spontaneously hypertensive rats. We therefore tested the hypothesis that elevated plasma BNP levels predict the onset of hypertension in normotensive subjects. Japanese normotensive participants who were at our hospital for a yearly physical check-up (mean age 52.7 years, 35.9% women, n =5,026) were enrolled in the study. Blood pressure and BNP were measured at baseline and subjects were followed up for 5 years (median 1,114 d), with the endpoint being the development of hypertension. We evaluated the relationship between plasma BNP levels at baseline and the incidence of hypertension during the follow-up period.