A number of microfabricated flow cytometry devices have been proposed based on electrical(1,2) or optical(3) detection techniques. On chip marker-free differentiation of cells using impedance spectroscopy was demonstrated between leukocyte sub-populations and on erythrocytes+ghosts mixtures.(4) The detection part of the chip includes 4 microelectrodes patterned on the top and bottom walls of a rectangular microchannel which define two detection volumes (Figure 1). Although preliminary results showed the potential of the impedance measurement using specific frequencies, a systemic approach is required to determine an optimal set of discrimination frequencies for cell sorting.