Multifrequency (1kHz-1MHz) impedance of human blood, from 8 donors, for the hematocrit range from 36% to 43.5%, is measured using the true four-probe technique. Cole-Cole parameters, that are characteristic of blood, are used to model the equivalent electrical circuit. Results are then applied to Fricke's theory of suspension of particles at f → 0 and f → ∞. Fricke's equation, so far, has been widely used at f → 0 in determining the shape factor for red cells or the hematocrit of blood samples. In this paper, it is shown that, solution of Fricke's equation of suspension at f → ∞ can be used in calculating the inside resistivity ρc of red cells. We suggest that ρc should replace the Cole-Cole parameter ρi. This parameter, together with Cole-Cole parameters might be a potential index for evaluating blood in clinical applications.