We tested the hypothesis that plasma brain natriuretic peptide (BNP) levels are elevated in patients with acute cerebrovascular diseases (CVD) independent of heart disease, and reflect CVD severity. After careful evaluations for heart disease, the study included 79 consecutive patients with CVD without any evidence of heart disease admitted within 48 h after onset (71+/-10 years), and 26 control subjects without CVD (CT, 67+/-12 years). Ischemic stroke subtypes were defined by the TOAST classification. Large-artery atherosclerosis (LAA, n=27), small-artery occlusion (SAO, n=27), and intracerebral hemorrhage (ICH, n=25) were included. The plasma BNP levels were measured at admission and 1 month later. Stroke severity and brain infarct volume were evaluated. There were no significant differences in the clinical profiles including echocardiographic parameters among the groups. The plasma BNP level (pg/mL) upon admission was higher in LAA (70.6+/-53.9) than in SAO (38.2+/-28.4) and CT (28.5+/-19.9) (both p<0.05). The level in ICH (47.3+/-28.6) was not significantly different from that in CT. The BNP level in ischemic stroke was positively correlated with the NIH Stroke Scale (NIHSS) (rho=0.42, p<0.05) and infarct volume (r=0.34, p<0.05). Brain infarct volume and NIHSS were independent contributors to the plasma BNP level in ischemic stroke. One month later, the BNP level was significantly decreased and was similar in all CVD groups. The plasma BNP level transiently increased in patients with LAA independently of heart disease, and reflected infarct volume and the severity of acute ischemic stroke.