Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Methods: Twenty-nine maintenance hemodialysis (HD) patients (16 males) underwent body composition analysis including whole body magnetic resonance imaging (MRI), whole body potassium (⁴⁰K) content, deuterium (D₂O), and sodium bromide (NaBr) dilution, and segmental and wrist-to-ankle BIS, all performed on the same day before a HD. . Segment-specific resistivity was determined from segmental fat free mass (FFM by MRI), hydration status of FFM (by D₂O and NaBr), tissue resistance (by SBIS) and segment length. Results: Segmental FFM was higher and extracellular hydration of FFM was lower in males compared with females. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV and total body water (TBW) from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body, did not differ significantly from gold standard measures. Conclusion: The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV and TBW. Use of segmental resistivity values combined with adjustment for body volume that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.