The principal distinction of tyrosine transport in the electromembrane system is revealed. It lies in the absence of electromigration of this amino acid through the cation-exchange membrane MC-40 in a wide range of current density. This is true for any pH value, including the region where tyrosine exists mainly in the form of cations. Only insignificant diffusive transfer of this aromatic amino acid (pI = .63) is observed. At the same time the dependence of the flux through the anion-exchange membrane on the current density has the traditional form for amino acids with the maximum corresponding to the limiting current. On the basis of the revealed regularity of tyrosine transport, we study the possibility of its separation from the basic amino acid (arginine or histidine) that migrates actively through the cation-exchange membrane.