BACKGROUND: The plasma concentration of atrial natriuretic peptide (ANP) has been shown to be a volume marker and be useful to predict cardiovascular disease in hemodialysis patients, so we investigate the association between 24-hour ambulatory blood pressure monitoring (ABPM) parameters and the plasma concentrations of ANP. METHODS: Plasma concentrations of ANP of 52 CAPD patients were measured and the patients were divided into the high ANP (>40 pg/mL) and the low ANP (<40 pg/mL) groups. We analyzed the association between the 24-hour ABPM parameters and the plasma concentrations of ANP of both groups. RESULTS: On a 24-hour ABPM record, a daytime mean systolic (167.1+/-22.4 vs. 142.2+/-23.5 mmHg, p<0.01) and diastolic (100.2+/-14.5 vs. 87.9+/-19.2 mmHg, p<0.05) blood pressure and a nighttime mean systolic (162.5+/-31.1 vs. 136.1+/-33.2 mmHg, p<0.01) and diastolic (94.3+/-16.8 vs. 84.3+/-14.9 mmHg, p<0.05) pressure were significantly increased in the high ANP group. In a simple linear regression analysis, daytime mean diastolic pressure was best correlated with the plasma concentrations of ANP (r=0.53, p<0.05). In peritoneal equilibrium test, a daytime mean systolic (168.7+/-18.1 vs. 128.4+/-11.8 mmHg, p=0.024) and diastolic (99.3+/-11.5 vs 80.3+/-8.3 mmHg, p=0.028) pressure were significantly increased in high transporter group. CONCLUSION: A 24-hour ABPM parameters are correlated with the concentrations of plasma ANP, so the plasma concentration of ANP may be useful for the assessment of the volume status and the treatment of hypertension in CAPD patients.