Body water and body fluid compartments evaluation is most important in human physiology and pathophysiology. Several sophisticated methods, from hydrostatic weighting to air displacement plethysmography, have been developed, although not so easy to apply. Bioimpedance based technologies have been extensively developed and are currently used from diagnostic (e.g. ECG) to various therapeutical procedures (e.g. iontophosesis). Recently, a bioempedance system was proposed to provide quantitative information, non invasively, about Total Body Water (TBW) Extracellular Water (ECW) and Intracellular Water (ICW) (among other variables). As known, these methods are very practical and easy to use, being based in the electrical properties of human tissues through the skin. By using different frequency ranges, appropriate correlations with biological variables are explored by specific mathematical algorithms. According with the manufacturer, TBW is calculated at 200kH, ECW at 5kHz and ICW is obtained from these two measurements. However, a clear demonstration of those relationships is not available. So, the authors tested, in the present paper, validity of bioimpedance data gathered from human volunteers, and relationship with reference plasma electrolytes known to determine or influence body fluid distribution. 32 healthy volunteers, both gender (6 male and 26 female) aged 21 to 82 (mean 36,16 + 17,46 years old) giving previous informed written consent, were selected during routine lab check up. All procedures fully respected Helsinky principles and respective amendments. This varied sample regarding age, diet habits and physical condition , is essential to validate the method. After inclusion, a venous blood sample was collected in order to determine Na+, K+ and Cl- concentrations (selective ions potenciometry). Body fluid compartments were than obtained by the Bodystat QuadScan 4000 (Bodystat UK) measurements involving the application of 2 electrodes according with the manufacturer specification. Results were compared by Pearson’s correlation test and by the qui-square test, and a 95% level of confidence adopted. Results confirmed the sample’s heterogeneous profile. TBW was highly correlated with weight and with the body mass index, and higher in males. Plasma ion concentration was within regular ranges in all volunteers. K+ correlated well with ICW while Na+ and Cl- correlated well with ECW. Nevertheless correlation between Na+ and ECW is reportedly more consistent than the correlation between CL- and ECW. In conclusion this work demonstrated this bioimpedance method is valid to measure the body water compartments, confirming that observed specificity, linearity, measurement range, and precison fully are consistent with the device application purposes.