Some studies have evaluated the volume status of PD patients in relation to modality transport status, residual renal function, or inflammation. However, whereas these studies contribute information on relative volume status in different groups of PD, they were hampered to express the degree of true fluid overload due to the lack of a reference population. In contrast, Wieskotten et al evaluated a large cohort of 688 healthy persons using the BCM to derive reference ranges, allowing to compare fluid overload as measured by BCM to age and gender matched values of the normal healthy population. In addition, expressing extracellular and intracellular water as absolute values induces the problem of scaling to body size. In previous studies using bio-impedance, ratios of extracellular water to height, weight, body surface area, intracellular water or total body water have been used to express “fluid overload”, but the ideal scaling parameter remains a matter of debate. The use of relative Dtissue hydrationdiminishes the problem of scaling nearly completely, and allows comparison to the healthy population. In HD patients relative Dtissue hydration is associated with mortality, indicating the clinical relevance of this parameter. The European Body Composition study in PD was designed to measure hydration status in a large, multicentric cohort of PD patients using the BCM device, as compared to a healthy reference population, and to establish associations between clinical and practice related parameters and volume status. The EuroBCM study is the first large multi-centre study of hydration status and its associated factors in PD patients in Europe allowing comparison to a healthy reference population. Fluid overload was a frequent finding in PD patients as compared to a healthy reference population, but comparable to that reported in HD patients. The deviation from the relation between blood pressure and tissue hydration was substantial, pointing out that blood pressure is not a good tool to evaluate hydration status in PD patients. Overhydration was associated with higher age, male gender, diabetes, lower BMI, higher systolic blood pressure, and use of hypertonic solutions, and in these conditions, physicians should have enhanced awareness for volume status. Use of LEE011 polyglucose or biocompatible glucose solutions or the type of PD modality was not independently associated with hydration status. In the large cohort of the EuroBCM in PD study, a substantial portion of patients were fluid overloaded by more than 1.1 litre, the 90th percentile of absolute Dtissue hydration in the normal reference population, and 25% of patients had a relativeD tissue hydration/extracellular water ratio above 15%, a value associated with increased mortality in HD patients. Substantial fluid overload is therefore indeed a prevalent problem in PD patients, and more attention should be given to its assessment and correction.