Adequate body hydration is considered the key element of fluid management in critically ill patients including group with end stage renal failure. Bioimpedance technique is widely used as a non-invasive, simple and accurate method to measure body composition. The purpose of the paper was to prescribe the using of single, and multifrequency bioimpedance spectroscopy technique for estimation of fluid balance in end-stage renal patients. We also discussed some measurements and data modelling problems, including postural change effect, and intercompartmental fluid shift during dynamic monitoring of fluid balance.