The aim of this study was to examine the possibility of increasing sodium and water removal with peritoneal dialysis. Ten patients aged 67.3 +/- 6.2 years, on continuous ambulatory peritoneal dialysis (CAPD) for 28.1 +/- 13.9 months, with no episodes of peritonitis for at least 2 months and clinically normohydrated, gave their informed consent to undergo two consecutive peritoneal equilibration tests (PETs) with dialysis solution at a sodium concentration of 126 mEq/L (low sodium) and 132 mEq/L (normal sodium), both with 2.5% glucose. Net ultrafiltration and sodium mass transfer were 319.4 +/- 178.5 and 443.2 +/- 234.4 mL (p = 0.0346) and 27.7 +/- 24.5 and 28.2 +/- 27.1 mEq (p = NS), respectively. There were no variations in natremia or the transport indices of the studied solutes or in the arterial pressure or heart rate. All patients showed drowsiness or torpor during the low sodium PET and one had cramps. The 126 mEq/L sodium dialysis solution showed no advantages compared to the more common solution, 132 mEq/L. However, further study is necessary to check the potentiality of solutions with different sodium and glucose compositions for both acute and chronic use.