It is well known that plasma brain natriuretic peptide (BNP) concentration is elevated in cardiovascular diseases such as congestive heart failure. However, although it has been reported to increase in hemodialysis (HD) patients, little is known about plasma BNP in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Plasma BNP concentrations were measured and compared among CAPD patients (n=32), HD patients (n=63) and healthy volunteers (n=14) as well as those patients without cardiovascular disease. In addition, the correlation between plasma BNP concentration and parameters of echocardiography was examined. Plasma BNP concentration was significantly higher in CAPD patients without cardiovascular disease (n=23) than in healthy volunteers (n=14) (62.1+/-60.6 pg/ml versus 9.7+/-9.7 pg/ml, mean +/- SD, P<0.0001). Furthermore, it had a positive correlation with LVMI (CAPD: r=0.37, P=0.0354; HD: r=0.49, P<0.0001) but a negative correlation with LVEF (CAPD: r=-0.39, P=0.0277; HD: r=-0.40, P=0.0010) in both CAPD and HD patients. When all patients were compared, plasma BNP concentration was significantly lower in CAPD patients (n=32) than in HD patients (n=63) (114.8+/-142.7 pg/ml versus 296.8+/-430.4 pg/ml, P<0.0001). When those patients without cardiovascular disease was compared, it was also significantly lower in CAPD patients (n=23) than in HD patients (n=40) (62.1+/-60.6 pg/ml versus 151.8+/-102.2 pg/ml, P<0.0001). In conclusion, plasma BNP concentration was elevated in CAPD patients and correlated with LVMI and LVEF, suggesting that plasma BNP in CAPD patients may be associated with left ventricular hypertrophy (LVH) and left ventricular systolic dysfunction. In addition, plasma BNP concentration was significantly lower in CAPD patients than in HD patients, suggesting that cardiac load in CAPD patients may be lower than that of HD patients.