The impact of glucose-free icodextrin (ID) for overnight dwell as compared to conventional glucose-containing dialysate (GD) on potassium (K+) metabolism in continuous ambulatory peritoneal dialysis (CAPD) patients has not yet been investigated. Serum K+ in a total of 255 stable patients (116 on GD and 139 on ID) on CAPD for more than 6 months and in 139 patients on ID before and after ID use (Pre-ID and Post-ID) were observed along with nutritional markers in a 2-year study period (Jan. 2006 to Dec. 2007). The prevalence of hypokalemia was similar between patients on GD and ID (16.7% vs 17.3%), but was lower on Post-ID than Pre-ID (17.3% vs 20.5%) without statistic significance. The mean serum K+ level was higher on ID than on GD (P<0.05) as well as Post-ID than Pre-ID (P<0.001). In the multivariate analysis, serum K+ levels were positively correlated with serum albumin, and creatinine in all patients (P<0.05), and ID-use in younger patients (age< or =56, P<0.001). Serum albumin, creatinine, total CO2, and body mass index were significantly higher on Post-ID than Pre-ID. Icodextrin dialysate for chronic overnight dwell could increase serum K+ levels and lower the prevalence of hypokalemia compared to conventional glucose-containing dialysate. The improved chronic K+ balance in CAPD patients on icodextrin could be related to enhanced nutritional status rather than its impact on acute intracellular K+ redistribution.