An aqueous two-phase system composed of polyethylene glycol, dextran, and a functional ligand carrier was developed which enabled the specific separation of animal cells. In the presence of more than 0.042 M NaCl, almost all the cells examined were distributed in the bottom phase and the interphase, whereas the ligand carrier (Eudragit) was distributed in the top phase. An antigen was conjugated to Eudragit and the ligand-conjugated carrier was added to polyethyleneglycol 8000-dextran T500 aqueous two-phase systems. Using the systems, hybridoma cells, which produce antibody against the conjugated antigen, could be separated to the top phase from the parental NS-1 cells. This separation procedure may be useful for the establishment of a hybridoma cell line.