Objective To explore the appropriate sodium concentration in dialysate for the incremental peritoneal dialysis. Method We calculated the appropriate sodium concentration in dialysate by using the three pore model for the description of transmembranous solute transport. Result Under the circumstances of a fixed salt removal and various urine volume, the appropriate sodium concentration in dialysate changed only slightly. If the patient increased salt intake by 2 grams per day, however, the sodium concentration in dialysate should be lowered by 8 mmol/L. Conclusion The appropriate sodium concentration in dialysate is influenced mainly by salt intake, but not by residual renal function. The more the salt intake, the lower is the sodium concentration in dialysate used. Patients should be encouraged to restrict salt intake to less than 6 gram per day.