To determine the recording site of potentials, marking techniques are very useful. Diffusion, pressure microinjection and iontophoresis can be employed as the means of, injection of dyes.The electrode marking technique with dyes such as Fastgreen FCF, Niagara Sky Blue and Alcian Blue was applied to investigate the intracellular potential of hair cells in the organ of Corti. Alcian Blue was the most suitable dye for marking among them, and the cell identification technique with Alcian Blue was discussed.