Aim: The aim of this study was to demonstrate the ability of widely used bioimpedance techniques to assess dry weight (DW) and to predict a state of normal hydration in haemodialysis patients whose post-dialysis weight had been gradually reduced from baseline in successive treatments over time. Methods: Calf bioimpedance spectroscopy (cBIS) was employed to determine DW (DWcBIS) as defined by flattening of an intradialytic continuously measured resistance curve and by normalized resistivity (nRho) being in the gender-specific normal range. The wECV/ TBW ratio was determined by ` classical' wrist-to-ankle whole body bioimpedance spectroscopy (wBIS); in addition, a novel whole body model (WBM) based on wBIS was used to predict normal hydration weight (NHWWBM). Results: Twenty-one haemodialysis patients were studied; 11 1 6 measurements were performed per patient. Nine patients reached DWcBIS (DWcBIS group), while 12 patients remained fluid-overloaded (non-DWcBIS group). Change in wECV as measured by wBIS accounted for 46 1 23% in DWcBIS group, which was higher than in non-DWcBIS group (33 1 48%, P < 0.05) of actual weight loss at the end of study. In both groups the wECV/ TBW ratio did not change significantly between baseline and study end. Mean predicted NHWWBM at baseline was 3.55 1 1.6 kg higher than DWcBIS. The difference in DWcBIS and NHWWBM was 1.97 1 1.0 kg at study end. Conclusion: WBM could be useful to predict a target range of normal hydration weight particularly for patients with substantial fluid overload. The cBIS provides an accurate reference for the estimation of DW so that combined use of cBIS and WBM is promising and warrants further studies.