 Bioimpedance is recently known to be a reliable, reproducible and validated technic allowing determination of hydratation status in patients with chronic kidney disease treated with peritoneal dialysis PD. Overhydratation attested by bioimpedance is strongly associated with cardio-vascular morbidity and mortality in patients with PD. Overhydratation might concern more than half of patients at PD initiation, though the underlying mechanism remains unknown. 