Blood samples taken from healthy donors are diluted with 0.9% saline, to obtain samples with hematocrit values ranging from 31 to 50. Bio-impedance spectroscopy is then performed on these samples. Complex impedance measurements in the frequency range from 100 kHz to 1 MHz were fitted into Cole-Cole diagrams, using a LMS algorithm. Data were interpreted in terms of an equivalent resistor-capacitor circuit. In this hematocrit range, all four Cole-Cole parameters R/sub c/, R/sub i/, F/sub c/, and /spl alpha/, are shown to be a linear function of hematocrit. With increasing concentration of red blood cells, the intracellular conductivity is also increased while extracellular conductivity is reduced and, Cole-Cole plots are shifted upwards to the right, in the complex plane, indicating a higher /spl alpha/ and a lower F/sub c/. We suggest that, parameters R/sub c/, R/sub i/, F/sub c/, and /spl alpha/, are a potential index for clinically evaluating blood samples.