The aim of this study was to compare fluid state, ambulatory blood pressure, and sodiumremoval in automated peritoneal dialysis (APD) and continuous ambulatory peritonealdialysis (CAPD). This observational, cross-sectional study comprised 20 APD and 24 CAPD patients with a mean duration on peritoneal dialysis of 30+/-26 and 21 +/-23 months, respectively. Sixty-four percent of the patients were treated with icodextrin. The methods used were 24 hr dialysate and urine collections, standardized 3.86% glucose peritoneal equilibration test (PET), bioimpedance analysis, and 24 hr ambulatory blood pressure monitoring. Extracellular water (ECW) corrected for body weight was 0.23 6 0.03 L/kg both in APD and CAPD patients. The slope normovolemia value according to Chamney was 0.0 6 0.2 L/kg in APD patients and 0.0 6 0.05 L/kg in CAPD patients (not significant [NS]). Mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) were respectively, 132 +/- 25 and 79 +/- 8 mm Hg in APD and 129 +/- 16 and 76 +/- 11 mm Hg in CAPD patients (NS). Sodium concentration in dialysate was respectively, 129.5 +/- 3.5 mmol/L in APD and 132.4 +/- 4.1 mmol/L in CAPD (p= 0.017). Dialysate sodium removal was 80.6 +/- 78.4 mmol/24 hr in APD and 108.7 +/- 96.8 mmol/24 hr in CAPD patients (NS). Natriuresis was respectively, in APD 76.6 +/- 65.5 mmol/24 hr and in CAPD 93.5 +/- 61.7 mmol/24 hr (NS). Total sodium removal was 149.5 +/- 76.6 mmol/24 hr in APD and 198.4 +/- 75.0 mmol/24 hr in CAPD (p= .039). Despite a higher daily sodium removal in CAPD patients, fluid state and blood pressure were not different between APD and CAPD. In general, volume status and blood pressure appeared to be reasonably controlled in this unselected population.