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Background: The majority of haemodialysis (HD) patients gain weight between dialysis sessions and thereby become volume overloaded, whereas peritoneal dialysis (PD) is a more continuous technique. Cardiovascular mortality and hypertension is increased with both treatment modali-ties. We therefore wished to compare volume status in PD and HD to determine whether PD pa-tients are chronically volume overloaded, as a risk factor for cardiovascular mortality. Study De-sign, Setting and Participants: We retrospectively audited 72 healthy HD patients and 115 healthy PD patients attending a university hospital dialysis centre for routine outpatient treat-ment, who had multi-frequency bioimpedance measurements of extracellular water to total body water (ECW/TBW). Results: The groups were well matched for age, sex, weight and ethnic-ity, PD patients had greater urine output [1,075 (485–1,613) vs. 42.5 (0–1,020) ml/day, p ! 0.001], but there was no difference in antihypertensive prescription (63.5 vs. 76.4%), mean arterial blood pressure (post-dialysis 101.6 8 1.5 mm Hg vs. pre-dialysis 102 8 2.4 mm Hg), although post-di-alysis arterial blood pressure was lower than in PD patients (96.4 8 3.1 mm Hg, p ! 0.05). The ratio of ECW/TBW fell after HD (pre-dialysis 0.394 8 0.001 vs. post-dialysis 0.389 8 0.004, p