To determine the relationship between total body water (TBW) and local water content measured in the skin (SW) this study assessed 8 piglets in an over-hydration model. Total body water was assessed by deuterium oxide (D2O) dilution throughout the experiments, and by whole body carcass analysis at the end of each experiment. Additionally extracellular water and plasma volume were assessed using bromide dilution and Evan's blue, respectively. Skin water was assessed by tissue biopsies, taken at 60 min intervals throughout the experiment. Lean body water (LBW) and lean skin water (LSW) were assessed by extracting the fat from the carcass and biopsy samples. A correlation does exist between TBW and SW with r2=0.585 (P<0.05), however, the strongest correlation occurred between LBW and LSW with r2=0.8653 (P<0.05) and a standard error of prediction of 0.77%. These data demonstrate that LSW gives and accurate and precise estimate of LBW, and could therefore be used to determine the hydration index in appropriate research settings.