Whole body bioimpedance (BI) appears to be accurate and reproducible in the assessment of body composition, but does not appear useful for estimation of dry weight. Segmental BI has been used for the assessment of muscle mass in body segments, such as arms or legs and may be useful for rehabilitation studies. A promising new development is the application of segmental BI for dry weight determination. Changes in extracellular volume of the calf are recorded continuously during HD, thereby allowing the detection of a timepoint at which no further volume is removed from the calf despite ongoing ultrafiltration (UF). Continuation of UF beyond this point is associated with an increased risk of intradialytic hypotension. This new technology may help optimizing the prescription of dry weight and UF rates in hemodialysis patients.